REPORT ON THE ISOPODA. 135 



Family Anceid^e. 

 Anceus, 1 Eisso. 



Gnathia, Leach, Edin. Ency., vol. vii. 

 Anceus, Risso, Crust, d. Nice, p. 51, 1816. 

 Praniza, Leach, MSS. 



Anceus bathybius, F. E. Beddard (PL XVIII. fig. 1-7). 



Anceus bathybius, F. E. Beddard, Proc. Zool. Soc. Loud., 1886, pt. i. p. 119. 



Only a single representative of this genus, was dredged in deep water, and it consists 

 merely of a single fragment comprising the head and the thorax ; the abdomen has entirely 

 disappeared. 



The specimen is a male, and measures about 10 mm. in length. 



The head is squarish in outline and terminates anteriorly in a long obtusely pointed 

 rostrum, which has a tuft of hairs at its free extremity ; the dorsal surface of the head is 

 traversed by several shallow furrows. Eyes are completely absent. The first three of 

 the free thoracic segments are much shorter than the two following, but of about equal 

 width ; the first segment is shorter than the two next, which are subequal ; the fourth is 

 about equal in length to the second and third taken together ; the fifth is rather longer 

 again. The surface of the body is smooth and unmarked with spines or tubercles. 



The antennules are about as long as the rostrum ; they consist of three basal joints 

 and a flagellum of five joints ; the two proximal joints of the peduncle are short, the 

 distal joint is about equal in length to the two basal joints taken together. In the 

 flagellum the first joint is extremely minute, the second rather long, the three following 

 joints progressively decrease in length, the terminal joint being again extremely 

 minute. 



The antennae are longer than the antennules ; the peduncle is four-jointed ; the 

 first joint is moderately long, the second shorter ; the third and fourth joints are of 

 considerable length, the fourth being the longest ; the flagellum is short, about equal 

 in length to the last joint of the peduncle ; it consists of about six short slender joints. 



The mandibles have the usual structure characteristic of the males of this genus ; in 

 the present specimen they were extended forwards parallel with the longitudinal axis of 

 the body, and reached to a point rather beyond the end of the rostrum ; these appendages 

 are shown in fig. 1, 2, each is somewhat bent and terminates in a blunt tooth ; from the 

 inner side nearly halfway down is another tooth-like projection. 



1 There seems to be some difference of opinion as to the correct name to be applied to this genus ; I have here 

 followed Westwood and Spence Bate. I imagine that, strictly speaking, a new name ought to be employed, since 

 Gnathia and Anceus were applied to the male only and Praniza to the female. I am unwilling, however, to create a 

 new generic term for so well-known an animal. 



