NO. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 75 



what twisted. Trunk abruptly enlarged and slightly twisted, at right 

 angles with the neck; abdomen small and hemispherical, with a 

 pair of rudimentary anal laminae destitute of setae ; egg strings at- 

 tached laterally and nearer the dorsal surface; tightly coiled into a 

 spiral ; eggs numerous and uniseriate. 



Two pairs of minute antennae, second pair chelate; mouth parts 

 reduced to mere chitin knobs; proboscis small and nonretractile. 

 Four pairs of swimming legs, first two pairs close together, biramose, 

 rami one-jointed, third and fourth pairs removed a considerable dis- 

 tance and uniramose, all the rami armed with setae. 



Internal generic characters of female. — Bilateral symmetry dis- 

 torted ; esophagus inclined to the head axis and very short ; stomach 

 without lateral lobes or convolutions. Intestine very narrow through 

 the neck, but much enlarged in the trunk; rectum short, given off 

 from the dorsal, posterior corner of the intestine and somewhat in- 

 clined dorsally. 



Ovaries on the dorsal surface, nearer the posterior end, diagonal 

 to the trunk axis, and not much flattened; oviducts also diagonal to 

 the trunk axis but in the opposite direction to the ovaries, the one 

 on the side to which the neck is attached close to the ventral surface, 

 the other considerably elevated above it, but the two pass down 

 around the intestine on opposite sides. Cement glands both on the 

 side of the elevated oviduct and not parallel to each other either lat- 

 erally or vertically, but deviously curved, the glandular portion much 

 longer than the ducts and indistinctly segmented. Chitinogen laj'^er 

 of the body wall most developed in the trunk, especially at the pos- 

 terior end; no definite skin glands. 



Genus habitat. — This genus fastens to the eye of its host, burrow- 

 ing in from the outer surface and bringing the mouth in contact 

 with the blood vessels at the back of the eye. The head and neck 

 are completely chitinized and covered with a thick cyst, they show 

 both torsion and flexion. 



Tyye of the genus. — Phrixoceyhalus cincinnatus Wilson, mono- 

 typic. 



{Phrixocephalu^^ <t>pt.^6s, a bristling of the hair, and Ke<f)a\rj, the 

 head.) 



KEY TO THB SPECIES. 



1. Head with three pairs of latornl horns; necli witli two sets of liorns, 

 all branched; trunlc narrow oblong (30 mm.)* cincinnatus Wilson, 1908. 



1. Head with one pair of lateral horns, profusely branched; neck with one set 

 of simple horns; trunk broadly triangular (11 mm.) 



trianguhia, new species, p. 76. 



1. Head unknown ; neck with one set of tripartite horns and inserted in the 

 side of the trunk; the latter semioval in outline; egg strings widely di- 

 vergent (5 mm.) (livcrsus, new species, p. 77. 



1 Average total length of species. , 



