720 THE VOYAGE OF H.M.S. CHALLENGER. 



The pleopoda are not apparent in the undissected animal, except the sixth pan, which 

 is comparatively short, but foliaceous in character, and reaches to about half the length 

 of the telson, and is armed on the outer margin with a small sharp tooth. 



Rhomaleocaris, n. gen. 1 



Animal short and stout. Carapace dorsally round and smooth, anteriorly produced 

 to a short straight rostrum, smooth on the upper surface, slightly dentate on the lower 

 near the apex. Frontal margin produced to a strong tooth between the ophthalmopoda 

 and antennae ; fronto-lateral angle produced to a point. 



Pleon short, smooth ; third somite the longest, and dorsally arcuate near its centre. 

 Sixth somite short. Telson tapering. 



Ophthalmopoda short and stout. 



First pair of antennas short, thick, and biramose. 



Second pair of antennae stout, and furnished with a short scaphocerite that is armed 

 with a tooth on the outer margin. 



First two pairs of pereiopoda chelate, and subequal in size. The three succeeding 

 j)airs short, robust, and simple, the posterior pair being a little the longest. 



Observations. — It is difficult to determine the position of this genus in relation to the 

 others. The specimens upon which it is founded are undoubtedly in an immature 

 condition, and it is almost certain that several of the parts will become altered in relation 

 to the rest in a very considerable degree. The flagella of both pairs of antennas will 

 probably become longer, the chelae of the first two pairs of pereiopoda will acquire a more 

 decided form, and the dactylos of the three posterior pairs of pereiopoda will possess 

 a more distinct unguiculate character. Yet there are other parts which, however much 

 they may vary, must still retain the generic characters, and these I have selected for 

 the description of the genus. 



Rhomaleocaris hamulus, n. sp. (PI. CXIII. fig. 2). 



Carapace one-fourth the length of the animal, smooth, anteriorly produced to a short 

 lanceolate rostrum, serrate on the lower margin, and having the orbital tooth anteriorly 

 produced to quite half the length of the ophthalmopod. 



Pleon having the somites short and deep. Third somite dorsally arcuate and 

 longer than the sixth. Sixth somite longer than the fifth, and not so long as the 

 telson. 



1 puficthio;, robust ; Kttgls, a shrimp. 



