NO. 1788. NORTH AMERICAN EROASILID.^— WILSON. 387 



for which the author would propose the name Phagus. At present, 

 however, the genus must be regarded as more or less provisional, 

 since the distinctions on which it is founded require confirmation by- 

 further study (see p. 391). 



That the maxillary hooks found in this subfamily are not the homo- 

 logs of the maxillipeds in Bomolochus, as some authors have described 

 them, is self-evident when once the mandibles and maxillae are cor- 

 rectly located. That they are homologous with the corresponding 

 hooks in Caligus and Lepeophiheirus , as Heller and Brian suggest, 

 is shown by their identity in structure, by their articulation directly 

 to the ventral surface of the head, by their sex variation, being larger 

 and longer in the male, and by their position. They appear relatively 

 farther forward than in many Caligus species, but even there they 

 are opposite the bases of the second antennae and in front of the 

 other mouth-parts, which is exactly their position here. And as 

 their presence is one of the things that shows the Caliginae to be the 

 least degenerate family of the Caligidge, so their presence here tes- 

 tifies that the Tgeniacanthinse is the subfamily showing least degener- 

 ation among the Ergasilidae. This fact is still further attested by 

 the presence of so degenerate a form as Tucca in one of the other 

 subfamilies. 



Genus TyENIACANTHUS Sumpf. 



Tseniacanthus carcharix, Sumpf, 1871, pp. 7-18, pis. 1 and 2. 



Female. — Head joined with the first thorax segment; each of the 

 three following free segments somewhat enlarged so that the four 

 together make from one-half to four-fifths of the entire length. The 

 lateral margins on these segments are turned over ventrally, and 

 each of the four pairs of legs projects strongly from the ventral sur- 

 face. Fifth and genital segments more or less abruptly narrowed. 

 In T. carcharise these two segments with the abdomen form a sort 

 of dimmutive tail, one-fifth of the entire length, tapering angularly 

 backward, and inclined at an angle of about 30° to the anterior part 

 of the body. 



First antennae probably six-jointed as in other genera; the three 

 basal joints thoroughly fused and half the entire length. Second 

 antennae similar to those of Bomolochus. Mandibles bipartite. A 

 portion of the first maxillae in the form of prehensile hooks opposite 

 the bases of the second antennae, similar to those in Caligus and 

 LepeopMheirus . (Fig. 4.) First maxillae of the usual pattern and 

 armed with plumose setae. Second maxillae rudimentary; maxilli- 

 peds also rudimentary, the terminal claw the same length as the basal 

 jomt. Both rami of the first swimming legs widened, and well armed 

 with broad plumose setae. Egg-tubes narrow and elongate; eggs 

 minute. 



