226 DISCOVERY REPORTS 



somite, but the body is apparently straight in Gurney's larva. In both, the rostrum is slender and 

 unarmed and reaches beyond the eyes for about the length of the eye, the antennal scale reaches 

 nearly to the end of the inner antennular branch, there are as yet no chelae on the first and second legs, 

 there are very long setose exopods on the third maxillipede and on legs i and 2, in all cases longer than 

 the endopods, and there are no exopods on legs 3-5 which are as yet not fully developed but are all of 

 about equal length. The pleopods are small buds in Gurney's larva, but are slightly setose in the 

 present specimen which is at a later stage. The sixth abdominal somite is as long as the third to the 

 fifth inclusive. The sides of somites 1-5 are slightly pointed. In the present larva the third abdominal 

 somite has a small median tooth and just behind it another tooth. These are apparently not present in 

 Gurney's larva. He gives no size for the latter. The present larva measures nearly 10 mm. in length 

 from the tip of the rostrum to the end of the telson, the antennular flagellum measuring 12-45 mm - m 

 length. The telson is nearly straight-sided, the end being slightly indented in the centre and rounded 

 on each side. It is armed with two pairs of dorso-lateral teeth and six setae terminally on each side of 

 a small knob, the outer tooth small, the inner teeth setose on the inside only. 



A comparison with known larvae of this sub-genus shows that it must belong here. Very little is 

 known of the larval stages of the sub-genus Periclimenes, genus Periclimenes. We do, however, know 

 one, the last larval stage of a form attributed with a query to Periclimenes {Periclimenes) longicaudatus 

 (Stimpson) (Gurney & Lebour, 1941, p. 146) which was followed through four moults to the third 

 stage and was shown to belong undoubtedly to this sub-genus. Lebour (1949a) described the newly 

 hatched larvae of Periclimenes {Periclimenes) iridescens Lebour. 



These are the only larvae so far known which undoubtedly belong to this sub-genus, and the late 

 larva differs much from Ancylocaris whose late larvae are also known. The features of these indicate 

 that they belong to some species of the sub-genus Periclimenes of the genus Periclimenes and a com- 

 parison with the last larva of P. longicaudatus {}), shows certain features in common. For example, 

 the body is bent at the third somite (as in the present larva), the fourth and fifth legs are short and 

 similar and there are no exopods on legs 3-5. This last feature is, however, perhaps not of generic 

 value as in many larvae of various genera, the number of exopods on the legs varies. The telson is of 

 a palaemonid type and very like that of the larva of P. longicaudatus {}), and also like some of the larvae 

 attributed in 1924 by Gurney to the Palaemonidae. 



It is of course impossible to be sure of the place of this larva, but it seems almost certain that it is a 

 palaemonid of the sub-family Pontoniinae and belongs to the genus Periclimenes sub-genus Peri- 

 climenes. There are several species of this sub-genus recorded from West Africa, but it may quite 

 likely belong to a new species. 



Thalassinidea 

 Callianassidae 



Occurrence (Stations). WS 979, 50-0 m., 15 Callianassa larvae, stages I-V. WS 979, 100-50 m., 

 1 Callianassa larva, stage I. WS 980, 100-50 m., 2 Callianassa larvae, early. WS 998, 50-0 m., 

 25 Callianassa larvae, stages I-V. WS 998, 100-50 m., 1 Callianassa larva, stage I. WS 998, 175- 

 100 m., 1 Callianassa larva, stage I. WS 999, 50-0 m., 9 Callianassa larvae, stages II— I II . WS 999, 

 100-50 m., 1 Callianassa larva, stage III. WS 999, 150-100 m., 1 Callianassa larva, stage V. 

 WS 1001, 50-100 m., 28 Callianassa larvae, stages I-V. WS 1001, 100-50 m., 4 Callianassa larvae, 

 stages I— III. WS 1002, 50-0 m., 7 Callianassa larvae, stages I-IV. 



A large number of Callianassa larvae (Fig. 2) were obtained, apparently all of the same species, but 

 varying from stage I to stage V. They are of the type I of Gurney (1942) to which C. subterranea 

 belongs (sub-genus Cheramus). The sub-genus Trypaea has a similar larva, those of T. affinis from 



