valves, uniform, strong, not dichotomous radials, and subequal ears with a moderately deep notch. P. amuriensis is much smaller in size and has unequal valves, the right flattened and practically smooth, the left inflated and strongly sculptured; also the unequal ears are joined to the shell without a separating canal, and the posterior edge meets the disc on a curve. The byssal notch is very deep. These features make the creation of a new genus necessary, so Mixtipecten is proposed with Pecten amuriensis Woods as type. Perhaps Cyclopecten is related to this Cretaceous stock.

The early Tertiary beds of New Zealand are not rich in Pectens, but in the Otoraran they are much commoner and larger. In Hutchinsonian, Awamoan, and younger beds the family is represented by many different specific groups sometimes containing very large individuals. One of the earliest is P. devinctus, which has subequal valves traversed by high, broad, radial ribs, the interspaces with waved radial threads. Supposed descendants are diffluxus, wollastoni (= sectus), and allani. These shells have still subequal valves though the left may be slightly less inflated; the sculpture consists of strong, high radials which tend to anastomoze with age; and the rib-interspaces have fine, regular, concentric ridges. The ears are fairly large, right-angled, subequal; byssal sinus definite but not deep. P. crawfordi which appeared in Lower Pliocene times may be a development from P. diffluxus by increased splitting of the radials. The ears are similar but the left valve is much flatter than the right, and the folding of the disc is stronger. Suter's use of Patinopecten for these shells is not to be recommended. P. caurinus Gould, the genotype, has large flat valves, the ears set on them without a separating channel; also the byssal notch is wide and deep. None of the major divisions of the Pectinidae agrees well with these New Zealand shells so the new genus Sectipecten is proposed with Pecten wollastoni Finlay (= P. sectus Hutton) as type.

The Mid-Tertiary P. athleta Zittel may be an offishoot from the main Sectipecten line of descent. The valves are equally inflated; but the radial ribs are rounded and the concentric ridges are irregular both in strength and disposition. The byssal notch is very deep and the right valve has narrow, paired, primary radials, whereas the left has broad, equally-spaced ones. These differences warrant the creation of the new subgenus Athlopecten with Pecten athleta Zittel as type. Suter's classification of this species under Pecten s. str. is offset by his placing under Patinopecten of P. marshalli which is very closely related to S. athleta. In Athlopecten the valves are equally inflated the left has broad ribs and the right, narrow, paired ones, in Pecten the right valve is much inflated and has broad ribs, the left is flat and has narrow ribs.

The ancestry of the Pliocene P. triphooki is not known. In this large shell the right valve is quite flat and the left is strongly convex. The sculpture consists of regular, radiating, fairly strong ribs, the interspaces with fine, even, concentric ridges. The ears are very large and subequal, the byssal notch being well marked, and the hinge-crura almost absent. The flattening of the right valve and the deep sinus may indicate relationship to Chlamys; but the absence of scales and the presence of fine regular concentric ridges as well as

the large posterior ears show that the relationship is not close. When the valves of a Pecten are unequally inflated, the most inflated valve has generally broader ribs than the flatter valve. Therefore the presence of broad ribs in the left valve of S. athleta perhaps means connection with P. triphooki. In any case relationship either to Chlamys or to Sectipecten is distant, so the new genus Phialopecten is proposed with Pecten triphooki as type. P. hilli and P. accrementus were, like P. triphooki, described from fragmentary material from the Napier limestone and are doubtfully separable from this species. Further collecting is needed to show the value of these divisions. Certainly a great number of forms are grouped round P. triphooki and several specific divisions are required.

The type of Euvola, P. ziczac L., has quite obsolete radial ribs in the right valve, with only linear interspaces, whereas P. novaezelandiae has strong ribs with wide interspaces. An ancestor of novaezelandiae from the Upper Pliocene of Castlecliff has very low rounded radials, but the interspaces are wide, and the shells are closer to Pecten s. str. Finlay (1926, p. 451) has recently proposed P. novaezelandiae as type of a new division, Notovola, because of the weak hinge-crura, flat or concave left valve “and the right valve also has none of the secondary ridges characteristic of Pecten maximus L., the type of Pecten, the ribs are higher and flatter, and the interstices deeper, smooth and narrower.” P. laqueatus Sowerby (Pliocene and Recent of Japan) agrees in all respects with P. novaezelandiae except that it has twelve instead of sixteen ribs. Also P. bellus Conrad (Pliocene of California) and P. larteti Tournouer (Helvetian of Aquitaine) may belong to the group. Notovola is quite as distinct from Pecten s. str. as is Euvola and is therefore used here as a subgenus of Pecten.

The typical Chlamys is well represented in New Zealand, especially from about the Oligocene onward, indeed the shell figured by Trechmann (1918, pl. 21, fig. 18) from the Trias of Nugget Point, might belong to this division. From Suter's list the following species should be transferred to other groups: uttleyi (aldingensis of Suter) to Serripecten (Janupecten); semiplicatus and dendyi to Pallium (? Felipes); hilli to Phialopecten. The Ototaran P. venosus, which has not yet been figured, is a Chlamys so its classification under Patinopecten was wide of the mark. Suter did not see a specimen when he revised Hutton's types, but one of the types, a right valve, has since come to light. The shell is small, about 1 ½ inches in diameter, and has from 10 to 12 smooth, rounded radials. The interspaces, about as wide as the ribs, but flat, are also smooth for the first inch. On the last half inch they contain about four scaly threads. A left valve collected from tuffs in the Ototara limestone by Professor Park in 1916 is much flatter than the right valve, and the scaly threads are present on the ribs as well as in the interspaces. The ears are subequal and acute, with fine scaly threads. This shell probably represents an offshoot from Chlamys which proceeded but a short way from the main stock, for we do not know of any descendants in later deposits.

The specimens on which the Californian P. andersoni Arnold was identified in New Zealand (Morgan 1911, p. 72) are casts: but they

are not that species, for the ribs divide at about an inch from the apex. As far as can be seen they belong to a new species and perhaps a new group, not closely related to any known New Zealand shell.

The type of P. scandula has not yet turned up, and no topotypes have been encountered, so that nothing definite can be said about this species. From Hutton's description, however, it seems fairly sure that he was dealing with a Chlamys s. str.

Pallium in a wide sense represents one of the major divisions of the Pectinidae, its members being widely distributed. The typical species P. plica Lamarck, from the Chinese seas, has strong hinge-crura, so that the New Zealand shells do not fit well into Pallium s. str. The subdivisions of the genus are extremely confused and badly need monographing. Dall (1898, p. 696) mentions Felipes Locard, Peplum Bucquoy, Dautzenberg, and Dollfuss, and Flexopecten Sacco. Nodipecten Dall and Lyropecten Conrad given by Dall as independent sections are also related. Cossmann (1914, p. 312) under the genus Chlamys recognised the subgenus Manupecten Montrs. 1889 (= Felipes Carus 1889) containing the section Flexopecten Sacco, but did not mention Felipes Locard. It is possible that one or all of the New Zealand species belong to an already separated division, perhaps to Felipes, so for the present Pallium, sensw lato, is recommended.

Pecten beethami and P. hutchinsoni belong to a group that lived in New Zealand seas during the early and middle Tertiary. The sculpture is not like that of any other division of the family, for the inflated right valve has over thirty peculiarly-bevelled, scaly, primary radials, whereas the left valve is crowded with from 60 to 80 fine, scaly, radial threads. The earliest known example is a left valve from the Waihao greensand at McCulloughs Bridge (Upper Eocene); somewhat later comes “Chlamys” enfieldensis Marwick from the Waiarekan. By Hutchinsonian times the shells had increased greatly in size, P. beethami being often over 6 ins. in diameter. Awamoan examples are much the same as the Hutchinsonian ones, but about this time the whole group apparently died out. P. yahlensis Tenison-Woods, from the Janjukian of Victoria, is an Australian representative agreeing closely with the typical P. hutchinsoni except in having weaker sculpture. The group has perhaps descended from an early Chlamys, but it is not closely connected with any known genus of the Pectinidae so the new genus Serripecten is proposed with P. hutchinsoni Hutton as type.

Serripecten seems to have an innate tendency towards obsolescence of the sculpture. Thus McCoy (1876, p. 13) described a species P. yahlensis var. semi-laevis with a smooth right valve. In New Zealand are a number of species showing smoothing of the left valve, or of both valves, but none in which the right has proceeded further along this road than the left. P. uttleyi Marwick (1924, p. 325) is a good example of this loss of sculpture. Considerable variation is met with in this shell, but some right valves show clearly the resemblance to Serripecten. P. hochstetteri Zittel as interpreted by Park and Suter (but not by Hutton) also belongs to this group, as was noticed by Tate. Other specimens from several localities of Otoraran

and Huthinsonian age show this smoothing of the left valve, and supply clear links with Serripecten. It is certain that the tendency extended over a long period, and so all shells with weak sculpture in the left valve are not necessarily directly related. In P. uttleyi, however, the obsolescence of sculpture has gone so far that the general appearance of the shell is quite different; consequently the new subgenus Janupecten with P. uttleyi as type is proposed. The ribbed shell included in Zittel's P. hochstetteri, and named below S. polemicus, can also be classed as Janupecten.

When Zittel (1864, p. 50) described P. hochstetteri, he had material belonging to two species, the first with two smooth, shining valves, the second with the left valve finely concentrically striated and the right with obsolete radials. That this was so can be proved by several lines of evidence. Thus his figures, supposed to show a right and a left valve are really of two right valves. Also in his description he says the left valve is “laevigata, interdum striis concentricis ornata.” This includes the two species, for the shell with a radially ribbed right valve always has a concentrically striated left valve, not a smooth one; though, as pointed out to me by Dr. Finlay, this could refer to weathered material of the ribbed species. The localities given by Zittel are Whaingaroa and Aotea, Auckland; and Cape Farewell, Nelson. At Whaingaroa and Aotea both species occur, but at Cape Farewell only the smooth shell is found. The evidence of the localities alone shows that two species were confused; and since the locality is a vital part of a description, it cannot be assumed that Zittel's description applies to only one species. Further, Zittel said that the left valve was smooth or concentrically striate, and the right valve weakly ribbed. The statement, as it stands, applies to the ribbed shell accurately enough; but quite possibly this agreement is apparent only. Whether Zittel regarded the byssal notch as anterior or posterior is not clear. At the time he wrote, opinion was divided on the subject, and the descriptions of other species in the “Novara” publication are not conclusive. The evidence afforded by P. athleta, however, seems to indicate that Zittel's left valve was what we call the right. Also, fig. 5a of P. hochstetteri, said by him to be a left valve, shows the byssal sinus plainly, whereas in the original of fig. 5b the ears are badly broken. This tends to show that the smooth right valve figured by Zittel was used by him for his description of the supposed “left” valve, and was not mistaken by him for a true left valve in the modern sense. At all events, there can be no doubt that Zittel handled two species and that his description and figures include both. Therefore, when Hutton (1873, p. 30) selected the shell with two smooth valves as hochstetteri and expressly excluded the ribbed shell he was quite within his rights, and the choice cannot be altered. His reference is “Zittel, Voy. Novara, Palae., p. 50, pl. XI, f. 5a, not 5b.” This course was approved by Tate (1886, p. 114) who correctly stated that the shell having a ribbed valve was apparently related to P. yahlensis T. Woods.

Hutton's deliberate choice of the smooth shell for P. hochstetteri was overlooked by Park (1905, p. 485) who took it for granted that P. hochstetteri should refer to the ribbed one (Zittel, pl. 11, f, 5b)

and gave the name Pseudamussium huttoni to the smooth. P. huttoni is therefore a synonym of P. hochstetteri and the latter must be used. The species with a weakly-ribbed right valve and a concentrically-lined left one being without a name, Serripecten polemicus is proposed, and a specimen from loc. 993, coast, section 70, block 19, Whaingaroa Survey District, is chosen as type.

The origin and relationships of P. hochstetteri are not clear. The small, smooth, Cretaceous shell identified by Woods as P. membranaceus Nilss. has no byssal notch, but otherwise closely resembles P. hochstetteri, and may well be ancestral. On the other hand it is possible that the smooth valves result from obsolescence of sculpture as in Janupecten; but more collecting is needed to settle this point. Suter's species P. waihaoensis is almost certainly closely related to the P. hochstetteri stock, for the ribs in the right valve are extremely weak, though whether obsolete or rudimentary cannot be determined. Perhaps a connection exists through this species with P. devinctus.

Occurring in the same locality as P. waihaoensis, i.e., Waihao Downs (Eocene) is an unnamed species with both valves smooth, and at McCullochs Bridge is yet another species distinct from P. hochstetteri. Probably many other species exist in the Oligocene and Miocene of New Zealand and have been lumped in with P. hochstetteri; but much more material is required to make satisfactory divisions. For the present, it is advisable to treat all New Zealand Tertiary Pectens with two smooth valves as belonging to one generic stock, though it is not certain that they do. For this group the new genus Lentipecten is proposed with type Pecten hochstetteri Zittel (Pl. 11, fig. 5a, as limited by Hutton P. huttoni Park).

The prominent ribbing on the left valves of P. waihaoensis and P. imperfectum seems worth subgeneric recognition so Duplipecten is proposed, with type P. waihaoensis Suter.

Suter apparently thought that the two valves of waihaoensis figured by him belonged to one individual, for his MS. label with them has the word “holotype” on it. We do not know what is the evidence for his opinion, and possibly another species related to L. hochstetteri is represented by the fragmentary right valve. Therefore the left valve (Suter, 1917, pl. 7, fig. 15) is here designated lecto-type of P. waihaoensis.

The Chatham Island Tertiary P. hectori has no known close relatives in the New Zealand region, but it agrees very well with the east North American Placopecten. This resemblance might be due to convergence, but since there is no evidence to connect P. hectori with any species of the south-west Pacific, Placopecten can be used, at least until more is known on the subject.

Until now, all internally-ribbed shells in Australia and New Zealand have been called Pecten, or Amussium, zitteli; but there are two quite distinct groups in the Tertiary of both countries. One has both valves similar and almost smooth with subequal ears not showing a byssal sinus, whereas the other has discrepant valves, the left with well-marked radial sculpture and the right with concentric only, also the byssal notch is well developed. Hochstetter (1864, p. 53, pl. 19, figs. 1b, 3 under Pecten sp. described the cast of a shell with

obtusely angled ears from Papakura (30 mm. high according to the figure). Later, on the same page, he mentioned a small shell from Orakei Bay (8 mm. high) as perhaps belonging to the same species. An internal cast was figured (pl. 9, fig. 1b) and on the same block are four other shells of similar size. Three of these are smooth, and one indicates by the unequal ears that it is a right valve. They were named P. aucklandicus. The remaining specimen shows the exterior of a shell with radial ribs and ears of about the same size as those of the Amussium and the P. aucklandicus. Zittel thought it might be P. fischeri, but neither the apical angle nor the number of ribs corresponds. The right ear is shown in the figure slightly larger than the left, but the shell is probably not a right valve for there is no sign of a byssal notch. This brings us to the question of whether all these shells might not belong to one species of Variamussium. Only an examination of the type or of topotype material will settle this.

Hutton (1873, p. 32), with material from several localities, gave the name Pecten zitteli to these internally-ribbed shells and referred to Zittel p. 53, though not to any figure. He described the shells as smooth and with cars equal and obtuse, height 0.85 inch (= 22 mm.).

Tate (1886, p. 115, pl. 7, figs. 3 a-c) ascribed to P. zitteli Hutton specimens from five Australian localities, giving as dimensions 10 mm. × 9.5 mm. His excellent material showed discrepant sculpture. on the two valves, so he gave a full description and figures, and thought that Hutton was wrong in saying that both valves were smooth.

The type of P. zitteli was not chosen until Suter (1914, p. 44, pl. 6. figs. 5 a, b) selected Hutton's specimen from Whangape Lake. The figure published by Suter is from an old, idealized drawing by Buchanan, probably from the type which has the measurements given by Hutton. The valves are not smooth, however, having fine concentric sculpture, but there are no external radials. Suter's description is only a quotation of Tate's, following that author's mistaken idea of which was the right and which the left valve. It is therefore based on a shell quite different from A. zitteli and requiring a new name.

Tate was right in saying that some New Zealand shells showed discrepant sculpture, but they are without a name unless indeed they are Zittel's P. aucklandicus.

The true P. zitteli appears to agree with Parvamussium Sacco; but I have not had access to Sacco's work or to specimens of the genotype, P. duodecimlamellatus Bronn.

The shells with discrepant sculpture can be classed as Variamussium Sacco type Amussium cancellatum E. A. Smith (fide Cossmann. Dall, following Verill and Busch, gave “Schmidt” and could not identify the shell).

Clarke's species A. papakurense, established because of the inequilateral shape, may be the same as A. zitteli. The present shape is probably due in large part to rock distortion.

Much confusion exists as to the spelling of Amussium and the many derived words such as Pseudamussium, Parvamussium, etc. Bolten's original spelling is Amusium, and this form has been followed by Dall and most modern American writers. Many European authors,