520 



BULLETIN" 15 8, UNITED STATES NATIONAL MUSEUM 



Distribution. — Kattegat, Greenland (Kr0yer) ; Belgian coast 

 (Beneden) ; English seas (T. and A. Scott) ; Skager Rak (Olsson) ; 

 Massachusetts coast (Rathbun). 



Color. — Body of preserved specimens a uniform brownish yellow. 



Female. — Head and neck as long as the trunk and of the same 



diameter throughout ; carapace squarely truncated anteriorly. Trunk 



three times as long as wide ; a single pair of posterior processes, small, 



conical, and ventral to the ovisacs. First antennae with enlarged 



bases and an apical tuft 

 of setae; second antennae 

 turned across the frontal 

 margin, the endopod 1-seg- 

 mented, with small spines 

 at the tip, the exopod 2-seg- 

 mented and tipped with 

 three spines ; second maxil- 

 lae cylindrical and tapered 

 distally; apical claw of 

 maxillipeds with two spines 

 on its inner margin. Length 

 of cephalothorax, 5-6 mm. ; 

 of trunk, 6-6.5 mm. 



Male. — Anterior end of 

 head squarely truncated, 

 turned at right angles to 

 the trunk axis and project- 

 ing ventrally beyond the 

 level of the trunk, the antennae and mouth parts arranged along the 

 truncated end. The trunk twice as long as wide, the caudal rami 

 short, conical, and pointed. Both rami of second antennae reduced 

 to mere knobs ; palp of first maxilla with a single seta ; second maxil- 

 lae no longer than the maxillipeds. Total length, 2 mm. 



Remarks. — This parasite in the present area is found only on the 

 gills of the halibut and can be recognized by its exceptionally large 

 size. 



Genus BRACHIELLA Cuvier, 1830 

 Female. — Cephalothorax elongate and cylindrical, usually flexed; 

 head enlarged and covered by a carapace. Trunk swollen, 

 depressed, and in the larger species with two rows of pit,s or grooves 

 on the dorsal and ventral surfaces; one or two pairs of posterior 

 processes and an unpaired genital process; no abdomen or caudal 

 rami. First antennae 2- to 4-segmented; second antennae biramose, 

 the exopod 2-segmented; second maxillae usually separate to their 

 tips, where they are joined to an ordinary bulla. 



Male. — Cephalothorax inclined to the trunk, from which it is sepa- 

 rated by a constriction, often by a short neck ; head with a carapace. 



Figure 308. — Parahrachiclla rostrata 

 lateral ; h, male, lateral 



a. Female, 



