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



the fourth and fifth are entirely respiratory, as in the genus Amphoroidea. This is the 

 ease with both sexes. 



The uropoda in the male (fig. 12) consist of a short fixed endopoditc and a long- 

 curved exopodite, which is very considerably longer than the caudal shield; in the 

 female (fig. 11) the uropoda are of a different shape; the two rami are subequal; the 

 outer movable ramus is narrower than the inner ramus, which is flattened out and pointed 

 at its extremity. 



Station 218, off New Guinea, March 1, 1875 ; hit. 2° 33' S., long. 144° 4' E.; depth, 

 1070 fathoms; bottom temperature 36°'4 F. ; blue mud. 



Family Cymothoid.e. 

 Anuropus, F. E. Beddard. 



Anuropus, F. E. LeddarJ, Proc. Zool. Soc. Lond., 1886, pt. i. ]>. 112. 



Definition. — Body very convex, smooth, without any hairs or spines. Head small, 

 without any trace of eyes. Thoracic segments subequal, furnished with well-developed 

 epimera except on the first segment, where they are fused with the te l- gum. Abdomen 

 narrower than thorax ; abdominal segments short and subequal, sixth segment larger and 

 rounded, flattened. Antennules very short, consisting of a basal joint and a swollen. 

 elongated, curved, distal joint ; antennas slender and well developed, with a four-jointed 

 peduncle and a flagellum of equal length. Thoracic appendages subsimilar, short and 

 stout, with a powerful terminal claw. Abdominal ajipendages all similar, consisting of a 

 short basal joint and two expanded foliaceous rami. 



Remarks. — This genus is quite the most remarkable that was obtained during the 

 voyage; it is represented only by a single individual from deep water (1070 fathoms) in 

 the Western Pacific, off New Guinea. In its general form there is no marked discrepancy 

 from other genera of Cymothoidre, to which family the present species is evidently to be 

 referred. The most remarkable divergence in structure, and one which is clearly corre- 

 lated with its habitat, is the modification of the abdominal appendages of the last pair. 

 One of the principal characteristics of the group Isopoda is the metamorphosis of one or 

 more pairs of the abdominal appendages into respiratory organs; the number of pairs of 

 limbs which are thus modified, and their form, is typical of different families. But in no 

 one genus or family do all the abdominal limbs serve the function of respiratory organs; 

 at least the terminal pair are modified into the rudimentary, styliform or flattened 

 appendages, which latter form together with the extremity of the abdomen a powerful 

 " caudal fin " the principal agent of progression. The present genus, therefore, in that 

 the terminal pair of abdominal appendages are precisely similar to the foregoing limbs, 

 evidently subserving like them the function of respiration, is quite unique not only in the 



