CEUSTACEANS FEOM THE TEOPICAL ATLANTIC. 355 



are equal in length to the first three of the pleon. These latter have the postero- 

 lateral angles well rounded. The next three segments of the pleon are short, together 

 scarcely longer than the third segment. The fifth and sixth segments are apparently 

 coalesced, and the telson seen in profile seems to be narrow, about equal in length to 

 the sixth segment. 



The eyes are small, consisting of about a dozen ocelli; the colour in spirit very pale. 



The first antennae are longer than the whole body from head to telson, with the first 

 joint or peduncle stout, not very much longer than broad. In the elongate, straight, 

 tapering flagellum no division could be discerned even near the apex. The inner 

 margin is fringed with numerous filaments, which when highly magnified are seen to 

 be broad and round-ended. The outer margin carries many spinules. 



The second antennae (of the female) are minute, planted near the hind margin of the 

 head, and only extending forward as far as the eyes. A trace of division into two or 

 three joints could rather be imagined than seen. 



The mouth-organs form a small, nearly circular, group, the pointed apex of the 

 epistome scarcely reaching halfway from the back to the front of the head. 



First gnatliopods. The side-plates of these and the following limbs are small and but 

 faintly distinguished. All the limbs of the perseon are exceedingly narrow, and the first 

 gnathopods are the shortest. Of its joints the second is the longest, the third the 

 shortest. The fourth, which is not twice as long as its breadth, is distinguished by an 

 armature of prickles. The fifth is longer than the sixth ; they carry a few setules, and 

 are together longer than the second joint; the sixth has a small tooth at the apex. 

 The finger is very slender, a little over half the length of the preceding joint. 



Second gnathopods. The branchial vesicles are small. The limbs are not very 

 different from the preceding pair, but with the second, fifth, and sixth joints longer, and 

 the fourth not prickly. 



First and second perceopods. The branchial vesicles are slightly larger than those of 

 the preceding, and smaller than those of the following limbs, those of the large third 

 peraeopods being the largest. These slender and unarmed limbs have all the joints, 

 except the third and seventh, longer than in the gnathopods, and the fourth joint 

 longer than the fifth. The finger is small. 



Third 2}erceopods. The elongate second joint is less than half the total length of the 

 limb, armed with spines on both margins, those on the front being the larger, and this 

 margin ending in a tooth which projects beyond the similar but smaller tooth of the 

 short third joint. The fourth joint is considerably longer than the fifth, the two 

 together being a little shorter than the second. The sixth is considerably shorter than 

 the fifth, and the finger is minute. 



Fourth perceopods. The branchial vesicles, though smaller than the preceding pair, 

 are larger than any of the others. The limbs are unarmed, more slender than the 

 preceding pair and shorter, but not very greatly so. The proportions of the joints are 



