Text-Fig. 1.—Nephrops challengeri, male, from 80–100 fathoms off Tora, New Zealand, 27/1/54. 1—Dorsal view (antennules and antennae not shown). 2—Lateral view of carapace and abdomen. 3A—Ventral view of the left 3rd maxilliped. B—Lateral view of dentate ridge on the dorsal surface of the ischium of the left 3rd maxilliped. (1 and 2 drawn to same scale.)

slightly depressed and with faintly indicated lateral carinae. The anterior region terminates in an acute point. The proximal half slopes ventrally, while the distal half is directed obliquely upward, so that the acute tip is situated on the level of the dorsal margin of the carapace. Just posterior to the middle of the rostrum, each dorsolateral margin is armed with a small lateral tooth directed anteriorly and obliquely upward. While the proximal half of the dorsal surface is concave above, the distal upturned half appears weakly carinate, the carinae gradually rising from just in front of the lateral teeth. The ventral margin is keeled, armed at the mid-point with an acute anteriorly directed tooth distal to, and e little longer than, the lateral teeth. The distal half of the ventral margin is carinate. The proximal half bears the two ventrolateral rows of ventrally directed setae between the eyes. The dorsolateral carinae of the rostrum are continued on

to the carapace as two parallel ridges, the postrostral ridges, which extend posteriorly almost to the cervical groove. These ridges are armed with 3 pairs of anteriorly directed teeth, the postrostral teeth, as in N. thomsoni, not 4 pairs as in N. sibogae. The first and largest pair of teeth are directed slightly upwards, as are the two posterior pairs, which are smaller, the 2nd pair being subequal to the lateral teeth of the rostrum, the 3rd pair being still smaller. There is a larger gap between the 1st and 2nd pairs than between the 2nd and 3rd. Just anterior to the 3rd pair there is a small pointed tubercle in the mid-dorsal line of the carapace, from which a low carina runs anteriorly to the rostrum and posteriorly almost to the cervical groove. This feature is also seen in N. thomsoni and N. sibogae. The two very small low tubercles described by de Man (1916) as occurring one on each side of the low dorsal carina between the bases of the anterior pair of teeth are present in a similar position on N. challengeri but are even more inconspicuous and can only be seen in the dried specimen. The depressed antennal tooth is large and acute and extends anteriorly almost as far as the anterior margin of the eye. Viewed dorsally, its outer margin, from near the hepatic groove, is almost parallel to the longitudinal axis and is but faintly curved laterally and anteriorly to the acute point, while the median margin is concave On a slightly lower level than the antennal spine, there is, immediately behind the hepatic groove, as in the two closely related species, a small acute anteriorly directed hepatic spine, subequal to the 3rd pair of postrostral teeth. The hepatic groove is quite distinct. It is directed dorsally, sloping towards the 3rd pair of postrostral teeth, but continues to only just beyond half way between the hepatic spine and the postrostral ridge. Immediately behind the upper termination of the groove there is another small anteriorly directed spine, subequal to the hepatic spine. As in N. sibogae there are no small spines along the posterior margin of the hepatic groove between the two hepatic spines described above. This feature clearly distinguishes N. challengeri from N. thomsoni, where there are four spines between the two hepatic spines. Between the upper hepatic spine and the orbit there are 3 other small, anteriorly directed spines as in N. sibogae, compared with 2 as in N. thomsoni. The most anterior one, just behind the orbital margin, is situated at one-third of the distance between the antennal spine and the postrostral ridge, and is directed very slightly dorsally. The next, the smallest, is situated a little further posteriorly on the carapace, at two-thirds the distance between the antennal spine and the postrostral ridge. The third is postero-ventral to the preceding spine and larger than the other two, being situated two-thirds of the distance between the first postrostral tooth and the upper hepatic spine. From the lower termination of the hepatic groove there are two small secondary grooves, one of which curves anteroventrally for about half the distance between the lower hepatic spine and the anteroventral margin of the carapace, while the other extends posteriorly as an inverted arc of a circle between the hepatic groove and the lower termination of the cervical groove. The deep and setose cervical groove curves anteroventrally from the dorsal margin of the carapace three-quarters of the distance towards the ventral margin. There is a low ridge along the mid-dorsal line of the cardiac region; at the anterior end of this ridge, rising immediately behind the cervical groove, is a pair of anteriorly directed spines a little smaller than the 3rd pair of postrostral teeth. The remainder of this ridge is quite smooth, lacking the prominent pairs of spines present on both N. sibogae and N. thomsoni. On each side of the mid-dorsal

ridge, the branchial region is traversed by three low obscure carinae, the sub-media the lateral and the lateroventral. These are extremely faint, being merely slight angles in the integument, but each carina terminates immediately posterior to the cervical groove in a small anteriorly directed spine and begins near the deep groove which divides the cardiac and branchial regions from the broad flattered band that borders the posterior margin of the carapace. This band continues, but is not as broad, around the posteroventral and ventral margins narrowing to vanish at the anteroventral angle. The very indistinct submedian carina begins about one quarter of the distance between the dorsal and ventral margins, and is straight, but slopes slightly ventrally to terminate in a small spine immediately posterior to the cervical groove. The lateral carina, slightly more distinct, is straight but slopes dorsally to terminate in a small spine about one-third of the distance between the dorsal and ventral margins of the carapace. The lateroventral carina, the most prominent, curves concavely from near the posteroventral angle of the carapace to terminate at a very small spine at the base of the cervical groove. This carina has slightly closer and coarser granulation than the surrounding parts of the carapace, which, though it appears almost smooth to the naked eye, is minutely granulated, especially on the branchial region.

The general shape of the terga and pleura of the abdomen closely resembles that described for N. thomsoni. The 2nd to 5th terga appear smooth and shining to the naked eye, there being no transverse groove on each side of the terga as in N. thomsoni, nor transverse row of shallow pits as in N. sibogae. The terga and pleura are, however, minutely pitted. The pleura of these somites are delineated from the terga by a low concave ridge, and have a central irregular sunken area. The delineating ridges of the 4th and 5th somites each bear a very small posteriorly directed spine near their posterior margins. As in both the other species the 6th somite of N. challengeri bears a small posteriorly directed spine in the mid-dorsal line of its posterior margin. The lateral ridge of this somite, which separates the tergum from the pleuron, appears finely serrated on its anterior half and ends in a small posteriorly directed spine nearer the posterior than the anterior margin. The posterodorsal margins of the pleura of this somite are each produced laterally into a posteriorly directed spine which overlaps the telson. This is square in shape with its posterior margin slightly convex and together with the uropods, is identical with that figured and described by Bate for N. thomsoni.

The flagella of the antennule are subequal to each other and to the carapace, the outer, however, appears more robust than the inner.

The flagella of the antenna and the peduncle together are just under five and one-half times as long as the carapace. The peduncle is a little less than two-thirds the length of the rostrum and bears a small sharp spine at the distal extremity of the curved lateral margin of the basipodite and another at the distal extremity of the median margin of the ischiopodite. The scaphocerite extending anteriorly as far as the distal end of die peduncle, is two-thirds as wide as long, and its lateral margin terminates in a small sharp spine, while its anterior margin curves gently and continuously into the median margin.

The mouth parts agree closely with those described for N. thomsoni, and except for the 3rd maxillipeds no further description of them will be given.

The 3rd maxillipeds extend anteriorly beyond the distal margins of the antennal peduncles. The ventral surface of the ischium broadens slightly distally, its lateral margin is distinctly concave, while the convex median margin is faintly serrated along its entire length but does not bear a small distal spine as in N. sibogae. The dorsal surface of this element is produced into a long transverse ridge armed with a single row of about 20 acute teeth. These teeth alternate in size, smaller teeth appearing between the larger ones, and there is a general increase in size distally with the row terminating in a single larger tooth. The merus is nearly as long as the ischium, and its median margin is armed with four acute spines of differing length, the distal spine being the largest. The carpus, with width a little less than half its length, does not bear an acute tooth at the termination of its ventral margin, as in N. sibogae. The propodus and dactylus are somewhat compressed, the former just over, and the latter just under, twice as long as broad.

The chelipeds or 1st pereiopods are large and prominent for the animal, but unlike other members of this genus are narrow and not swollen at the palms. They bear neither carinae nor rows of tubercles on their surfaces. The 1st leg on the left side is missing in the male described here, but in the other specimens the 1st legs are subequal. The right leg in this male is a little longer than the carapace and abdomen together. The ischium appears quite smooth both dorsally and ventrally but is, however, granulated on its median margin. The merus is compressed and flattened dorsally. It is armed with an acute, strong, terminal spine on the median margin and with a somewhat larger terminal spine on the dorsal surface. The lateral margin is produced as a blunt extension against the carpus. Both margins are granular, these granules being a little larger than those present on the dorsal surface; however the ventral surface is only weakly granulated. The cylindrical carpus, about half the length of the merus, is granulated all over. It bears three acute terminal spines, one at the extremity of the median margin, another on the margin of the dorsal surface, and a third, somewhat smaller, from the central convex extremity of the ventral surface. There is a fourth acute, distally directed spine at the centre of the lateral margin of the merus. No trace of the dorsal tubercle present on N. sibogae can be seen. The propodus three and one-half times as long as the carpus, does not widen appreciably at the articulation with the dactylus. The straight median margin is distinctly granulate, while the lateral margin is weakly convex and granulate, the remainder of the surface being only pitted. The dactylus or free finger, is a little more than half the length of the propodus and bears at the proximal end of its median or outer margin a small, anteriorly directed spine. Both fingers, somewhat flattened and gradually tapering distally, close tightly together, their obliquely and inwardly pointed acute tips crossing one another. The fixed finger is armed on the median margin with a large, subacute, dorso-ventrally compressed tooth, one-third of the distance between the distal end of the palm and the tip, and along almost its entire length to near the extremity with two rows of very much smaller teeth, alternating with still smaller ones Similar small teeth of differing sizes occur in a single row along the whole inner margin of the free finger, a few of the proximal ones being slightly larger than the rest. The single row of the free finger interlocks between the two rows of the fixed finger. Neither N. challengeri nor N. sibogae have a spine on the median margin of the palm, though one is present in N. thomsoni.

The 2nd to 5th pairs of legs are as described for the genus, the 2nd and 3rd pairs being chelate. The 2nd pair reaches anteriorly as far as the middle of the carpus of the 1st, the 3rd as far as the merocarpal articulation of the 1st, the 4th a little further and the 5th to just beyond the middle of the merus of the 1st.

The branchial formula of Nephrops challengeri is as follows:—

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This is the same as that given for N. thomsoni by Bate (1888) and for N. norwegicus by Bouvier (in Barnard, 1950). Alcock (1894) records a podobranch on the 2nd maxilliped of N. andamanicus and Holthuis (1945) states that this podobranch can be present or absent in N. norwegicus.

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The length of the rostrum is taken from the tip to the posterior margin of the orbit along the dorsal mid-line; that of the carapace, from the posterior margin of the orbit to the posterior margin of the carapace, along the dorsal mid-line. The depth of the carapace is taken just posterior to the cervical groove, while the width is taken through the branchial region. The measurement of the abdomen includes the telson and is not exact because of the difficulty of extending

preserved specimens. The total length is taken from the tip of the rostrum to the posterior margin of the telson. For the 1st pair of legs, the right member has been used Except in the case of specimen 2, where, because of damage, the left member was used.

Text-Fig. 2.—Nephrops challenger female, from 300 fathoms off the Chatham Islands, 3/2/54. Carapace, abdomen and left cheliped to show colour pattern.

Sexual Differences.

The female, from the Chatham Islands Expedition, is similar in all respects to the male described above, except, of course in the position of the genital apertures and the structure of the first two pairs of pleopods. No other sexual differences have been described for species of the genus Nephrops. The genital apertures are large and conspicuous in the female and are situated on the posterior portion of the coxopodites of the 3rd pair of legs, while in the male, where they are equally large and conspicuous, they are situated on raised tubercles on the posterior portion of the coxopodites of the 5th pair of legs. In the male the 1st pleopods are each modified into the standard type of reptant copulatory appendage, uniramous with styliform spoon-shaped terminal element. The 2nd pair of pleopods each bear a prominent expanded appendix masculina with a row of stiff setae along its median margin. The 1st pleopods of the female are much reduced and uniramous, while the 2nd pair are unmodified and similar to the succeeding pairs. The female was carrying about 250 eggs on its pleopods; these are subspherical with a diameter of 2.5 to 2.8 mm. (after preservation). They showed no sign of structure within, so were newly laid, indicating that the species breeds in the January and February period.

Colour Pattern.

The brilliant colour pattern of the Chatham Islands Expedition female was recorded before the specimen was preserved (Text-fig 2). My thanks are due to Dr. E. J. Batham, Director of the Portobello Marine Biological Station, who supplied me with the following Munsell notations for the major colours present.

The notation corresponding to the name used in the description below is as follows:

The anterior half of the rostrum is pink, while the remainder is white with a streak of bright red extending from just anterior to the 1st pair of postrostral teeth, around the base of the rostrum, and along the posterior margin of the orbit. The carapace has two broad saddles of brown across the dorsal, and extending part of the way down the lateral, surfaces. The anterior saddle extends dorsally from the 2nd pair of postrostral teeth to a point just anterior to the cervical groove, and laterally down to the posterior part of the base of the antennal tooth, with a small extension along part of the hepatic groove. The posterior saddle extends dorsally from the cervical groove to the deep groove separating the cardiac region from the broad flat posterior band of the carapace. This saddle extends laterally down the posterior margin of the cervical groove to fade out about midway between the two most ventral spines. There is a conspicuous band of bright red along the broad posterior band of the carapace extending a little on to the adjacent posterior edge of the branchial region and ceasing just dorsally to the rounded posteroventral angle. A small patch of pink on the posteroventral part of the branchial region is the only other colour on the carapace, the remainder being glossy white. In all the abdominal somites, the terga are brown while the pleura are pink, though there is a lot of intermingling of the two colours laterally. Each abdominal somite has a band of bright red along the posterior margin of the tergum, which extends more or less on to the posterior margin of the pleuron. The raised anterior margin of each of the terga of the 1st to 3rd somites, also bears a narrow band of bright red, extending in the 1st on to the anterior projection of the somite, which overlaps the posterior margin of the carapace. The telson and uropods are a uniform light red.

The eye is a clear bright yellow brown. In the 1st pair of legs the basis and ischium are white, the merus is white with a large patch of pink on the dorsal surface, and the carpus is bright red except for a small area around the terminal spines, this brightly coloured element being very conspicuous in the live animal. The palm and both fingers are white, except for a small patch of pink on the dorsal surface of the palm near the articulation of the free finger. The other legs are white with irregular longitudinal streaks of pink. The eggs stood out against this background of brown, white and red as a bright milky blue. As far as could be seen, the colour pattern of the “Maimai” male was identical with that of the female described above. Because this male specimen had been in formalin for several weeks before examination the colours had lost intensity, and the remainder of the animal had turned a general yellow brown.

References to colour in this genus are: Balss (1925) when he refers to N. andamanicus as being pinkish or reddish, with eggs sky-blue; Santucci (1932) who states that N. norwegicus is red with carpus of 1st pair of legs bright red; Boone (1938) when she describes the general colour of the body of N. norwegicus as pale flesh with deeper tones marking the pattern, light brown pubescence and eyes shining black, and Poulsen (1946) who describes the eggs of N. norwegicus