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



fairly well developed, those of the third and fourth segments rudimentary, of the fifth 

 absent ; females with two pairs of ovigerous appendages on the third and fourth segments, 

 those of the other segments (with the exception of the penultimate) absent. Eggs com- 

 paratively few in number, and of large size. 



The species are mostly of small size, and characterised by the shining polished 

 surface of their body and limbs. They are widely distributed, occurring at depths of about 

 100 to 700 fathoms, and many of the species appear to live among the branches of Corals, 

 their limbs being specially adapted for clinging. The atrophy of the caudal swimming 

 fin is carried to a greater extent than in either Ptychogaster or Eiimnnida, and it is 

 probable that the folding in of that part is a result of this condition in all three genera. 

 In one respect Uroptychus diflers from all other Galatheids, viz., in the presence of a 

 distinct movable acicle on the first free (in reality the second) joint of the antennal 

 peduncle, an imj^ortant and primitive character, but it must be remembered that a 

 similar process, though of very small size, is present also in Eumunida. In those species 

 which I have examined, the fifth arthrobranchia, counting from before backwards, is not 

 of larger size than the others, whereas in most of the Galathodea it is distinctly enlarged. 

 Professor A. Milne-Edwards has made known five species from the West Indies, dredged 

 during the " Blake " expedition, and more recently another species from the " Talisman " 

 dredgings in the North Atlantic. 



Uroptychus nitidus (A. Milne-Edwards) (PI. XXI. fig. 6). 



Diptychus nitidus, A. Milne-Edwards, Bull. Mus. Comp. Zool., vol. viii. No. 1, p. 62, 1880. 



Habitat. — Station 23, ofi" Sombrero Island, West Indies ; depth, 450 fathoms ; 

 bottom, Pteropod ooze. Two males, and a female with ova ; all of small size. 



Station 24, off Culebra Island, West Indies ; depth, 390 fathoms ; bottom, Pteropod 

 ooze. An adult male (figured), the body of which measures 34 mm. in length, and the 

 chelipedes 69 mm. 



The carapace is perfectly smooth and glabrous, with a single spinule placed on each 

 lateral margin at the antero-lateral angle. The rostrum is about twice the length 

 of the eye-stalks, with its margins entire, and it is slightly upturned towards the apex 

 (this last character being liable to considerable variation in difi"ereut specimens). The 

 chelipedes are broad, flattened, and of great length, with their surface smooth and 

 shining ; the merus narrows very considerably towards its proximal end, and a few 

 ill-defined granules occur, in some specimens at least, on its inner surface, while a minute 

 spinule is found on the upper surface and at the distal end of the ischium ; the fingers are 

 excavated inferiorly, and their surfaces are clad with delicate silky hairs ; two unequal teeth 

 are met with on the inner margin of the dactylus, and an ill-defined projection occurs on 

 the corresponding border of the immobile finger. The ambulatory limbs are slender, and 



