anterior ear with 5 strong scaly ribs; posterior ear very small, with about 4 weak, well spaced scaly ribs. Left valve similar to the right, but with about 20 ribs; a few posterior ones noticeably weaker; anterior ear with fairly straight outer edge, with 7 weak well-spaced scaly ribs a secondary in the two top interspaces; posterior ear with about 4 weak, widely spaced scaly radials.

Height 26 mm., length 22 mm., inflation (1 valve) 4.5 mm.

Localities: Flower-pot Harbour, Pitt Island; Momoe-a-toe.

Hutton gave as localities for his species “Chatham Islands; Castle Point, East Coast, Wellington; Broken River (L),” and when Suter (1914, p. 40, pl. 6, fig. 6) revised the old Geological Survey collection, he named the specimen from Broken River as type. This does not seem correct procedure, because the specific name chathamensis should by tautonymy be reserved for the Chatham Islands shell. Therefore a neotype (Fig. 18) from Flower-pot Harbour has been selected.

The strength of the scales on the ribs varies considerably, some specimens being almost smooth.

Chlamys seymouri n. sp. (Fig. 23.)

Shell large, thin, compressed, subcircular, slightly oblique. Apical angle acute, widening with age. Ears very unequal, anterior sinus deep. Sculpture: right valve with about 18 narrow primary ribs with very wide concave interstices with 8 and 10 or even more, scaly riblets of which two are often stronger than the others, these two appear on the sides of the primaries about 10 mm. from apex and the others follow later, their relative strength corresponding with their time of appearance; anterior ear with 4 scaly radials; posterior with 8. Left valve with about 20 narrow primaries, the wide concave interstices with two secondaries sometimes almost as strong as the primaries, each secondary interspace with 3 to 7 scaly riblets of irregular strength; anterior ear with about 15 spaced scaly radials of which 6 are stronger than the others, posterior with about 10.

Height 77 mm., length 73 mm., thickness (1 valve): 10 mm.

Localities: 1176, Momoe-a-toa; (?) Whenuataru Peninsula.

Remarks: Sometimes the primaries are smooth and much stronger than the interstitial riblets, giving the shell a resemblance to C. delicatula which, however, has more ribs. At other times the strength of the ribbing is very regular, making the shell look like a large C. radiata. Small specimens are often indistinguishable from C. radiata except by the vertical outer edge of the left anterior ear. C. seymour is a development of C. chathamensis in which there are many additional secondary riblets, all the radials having strong scales.

Chlamys mercuria n. sp. (Fig. 17.)

Shell small, ovate, strong, inflated, equilateral; ears very unequal: apical angle acute; right valve with 21 smooth, rounded, rather flat ribs with narrower interstices strongly marked with Camptonectes striation, anterior ear with a broad rib above and a narrow one below, left valve with about 22 radials narrower and stronger than those of right valve, interstices similarly striated.

Height 13 mm.; length 12 mm.; thickness (1 valve) 2.5 mm.

Locality: Waikaripi, below Wireless Station, Waitangi.

Chlamys titirangiensis n. sp. (Fig. 28.)

Shell of moderate size, subcircular, slightly inequilateral, apical angle about 95°, ears very unequal. Sculpture of right valve consisting of about 40 strong radial ribs many of them arranged in pairs and some double, the posterior and anterior ones noticeably finer; interstices somewhat narrower than the ribs and often with a central thread. Scaly concentric ridges are well developed in the interstices but are absent on the summits of the ribs (this may be due to wear). Anterior ear with five radials interstices crossed by spaced scaly ridges.

Height 37 mm.; length 36 mm.; thickness (1 valve) 6.5 mm.

Locality: Titirangi.

Pallium dendyi Hutton. (Fig. 29.)

1902. Pecten dendyi Hutton, Trans. N.Z. Inst., vol. 34, p. 196, pl. 8.

1915. Pecten (Chlamys) dendyi Hutton: Suter, N.Z. Geol. Surv. Pal. Bull. 3, p. 52.

The number of primary radial ribs is variable. Hutton's type with 9 in right valve and 8 in left is perhaps the commonest. On right valve the four strong central ribs are arranged in two pairs, each of which sometimes has the form of a single, broad rib with only a shallow indentation down centre. It is then extremely like P. convexum. In these cases, as a rule, the secondary ribbing is not strongly developed. The anterior primary rib in right valve is often not developed. The first or anterior rib is sometimes absent from left valve and there is considerable difference in strength of 6th rib.

Holotype in Canterbury Museum.

Dimensions of plesiotype, height 66 mm.; length 70 mm.; thickness of both valves 27 mm.

Locality: Momoe-a-toa.

Serripecten tiorioriensis n. sp. (Fig. 14.)

Shell rather small, fragile, subcircular, compressed, apical angle obtuse, inflation moderate, right probably more inflated than left; ears unequal; right valve with about 38 narrow, smooth, rounded ribs with smooth interstices of equal or slightly greater width. About 30 mm. from apex, ribs become sharp and scaly and a scaly riblet appears in each of the interstices, anterior ear with 5, posterior with 6 strong radials.

Height 41 mm.; length 42 mm.; thickness (right valve) 6 mm.

Locality: Tioriori.

Five good specimens were collected but all are right valves, consequently the left valve is unknown. The species is closely related to Serripecten hutchinsoni, but is much more primitive as the characters showing most resemblance appear at a late stage. It is at about the same stage as S. enfieldensis Marwick from the Waiarekan tuffs but has more primary ribs.

Sectipecten allani n. sp. (Figs. 13, 21.)

Shell large, strong, subcircular, apical angle obtuse, both valves inflated, right more than left. Ears unequal, anterior sinus shallow. Sculpture somewhat variable; type has in right valve 9 broad flat ribs, separated by interstices about half their width, the ribs have vertical sides and so their cross section is quadrangular, on their surfaces are faintly impressed from four to six broad secondary ribs. Interspaces have one strong narrow median rib throughout nearly the whole length, with weak one on each side coming in later. On anterior and posterior distal portions of disc are about five narrow radial riblets. Whole surface is covered with fine regular concentric ridges which in rib interspaces and on ears become much stronger and sharply raised, posterior ear with three obsolete, widely-spaced radials, anterior with 4 strong spaced radials and some secondaries. Left valve with 9 rather narrow, strong, rounded primary ribs which are weakly divided from about one inch from apex, some ribs have indications of still further division of each half. Interspaces are twice as wide as ribs, corresponding to the ribs of right valve; each has from 3 to 4 strong, rounded, secondary riblets, whole surface including ribs and ears covered by dense, sharp raised concentric growth-ridges.; each ear with about 3 obsolete radial threads.

Height 98 mm.; length 104 mm.; thickness of right valve 13 mm.; left valve 10 mm.

Locality: 1176, Momoe-a-toa.

Remarks: This is the largest and probably the commonest shell in the Pecten bed at this place. Some specimens reach 120 mm. in diameter. The inflated specimens have generally strong primary but weak secondary ribbing. Other shells have on the right valve rather weak primaries which are divided almost up to the apex, one or both limbs being grooved. These variations approach Sectipecten wollastoni Finlay (=sectus Hutt.); but in no case is strong primary ribbing accompanied by deep secondary grooving. The two species are closely related, but S. allani seems to be the less advanced, for the inflated adults are at about the stage represented by S. wollastoni of 30 mm. diameter.

Sectipecten toaensis n. sp. (Fig. 16.)

Shell rather small for the group, subcircular, somewhat compressed, apical angle 90°, valves almost equal, ears unequal, right valve with 33 strong regular quadrangular ribs separated by interstices of equal width, about 3 weak radial riblets anterior to primaries, interstices and sides of ribs crowded with sharp concentric ridges, near apex are shallow folds so weak that the number is uncertain, left valve with 35 somewhat irregular quadrangular ribs, there are 7 or 8 very weak folds the central one strongest, on summits of these folds the ribs are stronger than in interspaces, anterior ear with 6 sharp rough spaced radials, posterior with 7 smooth ones the top two stronger than others.

Height 49 mm.; length 47 mm.; thickness (l.v.) 9 mm., (r.v.) 8 mm.

Locality: Momoe-a-toa.

Remarks: Related to Sectipecten crawfordi which has the folds well developed and more ribs.