CEUSTACEANS EROM THE TE0P1CA.L ATLANTIC. 361 



more or less ciliated, filiform, some longer, some shorter than the first, but the 

 boundaries not always easy to detect, unless where the apical dilatation is seen 

 broadside on. 



The mouth-organs, as seen without dissection, show a broad and deep helmet-shaped 

 epistome, rather small mandibles with finely-toothed cutting-edges, the plates of the 

 maxillipeds elongate, with the apices not acute but rounded. 



The first gnathopods have a short spine at the apex of the third joint, prickles along 

 the hind margin of the fourth joint, and two spines at the apex; the fifth joint longer 

 and much broader than the sixth, beset with several sleuder spines ; the sixth joint 

 narrow, especially in the distal half, and beset with many spines ; the finger slender, 

 nearly straight, about half the length of the sixth joint. 



The second gnathopods have both the fifth and sixtli joints slender, the sixth 

 the longer. 



The first and second perseopods have the sixth joint much shorter than the fifth, 

 subequal in length to the fourth, but much narrower, with three minute spinules 

 indenting the distal half of the hind margin. The finger is curved, much shorter than 

 in the gnathopods. 



The third perseopods have the long second joint much broader than it is in any of 

 the other pairs, with its hind margin cut into about fourteen teeth, the front having 

 only the apical one, and that small ; the fourth joint is about three-quarters the length 

 of the second, the fifth two-thirds the length of the fourth, and the very slender sixth 

 a little shorter than the fifth. The finger is minute. 



The fourth peraeopods have the second joint three-quarters the length of that in the 

 preceding pair; the fourth, fifth, and sixth joints each subequal to the fifth in the 

 preceding pair and to each other, but the fifth slightly the longest of the three. The 

 finger is very small, yet longer than in the other perseopods. 



The fifth perseopods are small, but not strikingly slender. The second joint is 

 more than half the length of that in the fourth pair ; the fourth and fifth joints 

 are subequal, together longer than the second ; the sixth joint is much shorter and 

 narrower than the fifth. The finger is small, consisting of a bulbous base and a short 

 spine-like tip. 



The branchial vesicles are rather large, showing the cell-structure rather con- 

 spicuously. 



The pleopods have strong peduncles. The branches are shorter, with ten joints to 

 th? outer, and nine to the inner. 



The uropods have the peduncles longer than the coalesced inner ramus, considerably 

 in the second pair, less so in the first, and very slightly in the third. The first pair 

 have the inner ramus serrate along much of the outer margin, the outer ramus 

 resembling a considerable spine, equal to a fourth of the length of the inner ; the 

 second pair are serrate on the inner margin from a little above the commencement of 



