636 



THE VOYAGE OF H.M.S. CHALLENGER. 



The first pair of antennas carries a stylocerite that is sharp pointed and reaches beyond 

 the extremity of the first joint, the fiagella are both slender, and the longest is nearly 

 as long again as the rostrum. 



The second antennas carries a scaphocerite that tapers but slightly distally, and the 

 external tooth is subapical. 



The pereiopoda are moderately strong ; the meros in the three posterior pairs is 

 sparsely armed with strong teeth on the posterior margin, and the dactylos is cylindrical. 



The pleopoda increase in length posteriorly, and the outer branches of the last pair, 

 which help to form the tail fan, are a little longer than the telson. 



This species, which is represented by a single specimen, corresponds closely with the 

 figure of Heterocarpus Isevis given by A. Milne-Edwards, the chief distinction being that 

 Heterocarpus Isevis has a series of small teeth at the posterior extremity of the dorsal crest, 

 and the fiagella of the first pair of antennas are much shorter, reaching, according to 

 A. Milne-Edwards' figure, not beyond the extremity of the rostrum, whereas in Hetero- 

 carpus gibbosus they are unequal, one being a little longer than the rostrum, and the 

 other about twice the length. In Heterocarpus gibbosus the third somite of the pleon 

 is dorsally elevated into an elongated eminence, which gives the animal a more markedly 

 sinuous appearance than in Heterocarpus Isevis. 



Heterocarpus lievigatus, n. sp. (PI. CXII. fig. 3). 



Pleon dorsally free from large teeth. Carapace furnished with a central and two 

 lateral carinas, the median armed with four teeth on the dorsal crest and one on the 

 rostrum in advance of the orbit, anterior to which the rostrum is smooth and abruptly 

 elevated obliquely, and armed with six teeth on the lower margin, of which the anterior 

 is near the apex. The first lateral carina originates above and behind the outer orbital 

 tooth, and passes back to just within" the posterior margin of the carapace ; the second 

 carina commences in the fronto-lateral tooth and continues back for about two-thirds of 

 the length of the carapace. 



The first pair of antennas has one flagellum as long as, and the other twice the length 

 of, the rostrum. The second pair has the scaphocerite about half the length of the rostrum. 



The third somite of the pleon is furnished with a dorsal longitudinal tubercle, and the 

 telson is armed with four lateral and several terminal spines. 



Length, entire, .... 



of carapace, .... 

 of rostrum, .... 

 of pleon, .... 

 of third somite of pleon, 

 of sixth somite of pleon, 

 of telson, .... 



