PRAWNS FXIOM LAKK TANGANYIKA, 433 



appearance there was a striking resemljlance between them and 

 thepresont form, the larval chai-acter of which, however, is at once 

 ap{)arent hy the presence of well-developed natatory exopodites on 

 all the le<^s, except the la-st pair. 



The leatjth of the specimen examined was 2'(S0 mm., measured 

 from the tip of the rostrum to the enrl of tiio oaud;)! fan. 



The (jeneral form of the body (PI. JjlX. fiji^s. 1 & 2) is rather 

 slender and exhibits the chara(;tHristic Caridean aspect, the meta- 

 some being well fleveloped and diKtinctly lent in the middle. 



The carajmce has the dorsal face somcwliat flattened, with a 

 faint cervical sulcus in front of the middle and the posterior 

 edge emai-ginated dor-sally, exposing a part of the last segment of 

 the trunk. At the antero-lateral corners a small spine is seen, 

 somewhat remote from the margin. The rostrum in very small 

 and still quite simple, without any trace of denticles. 



The eyes are comparatively large and project considerably 

 beyond the lateral faces of the carapace. They arc distinctly 

 separated in the middle and freely mobile, being attached to each 

 side of a narrow transverse eminence located just beneath the 

 base of the rostrum. The corneal part is well <lefined from the 

 thickish pedicles, and has the visual elements very distinct. 



The limbs of the anterior division are complete in riumljer, five 

 pairs of true legs being present. All these, except the last pair, 

 carry outside natatory exopodites of the same structure as those 

 on the maxillipeds, making in all seven pairs of such appendages. 



The metasome is more tlian twice as long as the anterior 

 division anfl much more powerfully built than in the two pre- 

 ceding larva). On the five anterior segments the ei»imeral plates 

 are distinctly developed, though they do not as yet extend beyond 

 the ventral face of the segments. The 3rd segment is more 

 vaulted than the others and has the posterior edge somewhat 

 bowed in the middle, advancing over the base of the succeeding 

 segment. The 6th segment is very narrow, and considerably 

 longer than the two preceding segments combined. ]t carries at 

 the end a well-developed caudal fan, consisting of a median p-ece 

 (telson) and two movable lateral appendages (uropotla), each 

 divided into two setiferous lamellfe. The five preceding soirments 

 carry each a pair of ventral appendages (j)loopoda) exhiliiting all 

 the chief paits found in the adult animal, but these a|»pendages 

 seem not yet to have entered into function as swimming organs. 



Structure of the Appendages, 



The antenind<n (fig. 3) have the peduncle divided into three 

 well-defined joints, the first of which is much the largest and 

 exhibits outside near the base a lamellar expansion terminating 

 in a small anteriorly curving denticle. Some very delicate bristles 

 are seen issuing from the outer distal corner of this and the 

 succeeding joint, and from the inner corner of each of the two 

 outer joints a somewhat stronger plumose seta originates, pointing 



Piioc. ZooL. 80C.--1912, No.XXVlll, -JS 



