500 BULLETIlSr 15 8, UNITED STATES NATION" AL, MUSEUM 



some of the parasites. A. C. Weed obtained about 50 females, most 

 of which had at least one male attached, from the mouth of the 

 same fish in the public fish market, Washington, D. C, January 5, 

 1909. This indicates that the parasite remains on its host through 

 the winter, and practically all these females carried ovisacs. Often 

 the place of attachment is swollen into a papilla of soft puslike con- 

 sistency, in which the head and part of the thorax of the copepod are 

 immersed. 



Genus ACANTHOCHONDRIA Oakley, 1927 



Female. — Head separated from the first segment; first two seg- 

 ments free and bearing the two pairs of swimming legs; the last 

 three segments fused into a trunk which may be unsegmented, or 

 may be segmented once near its center. One pair of processes at the 

 posterior corners of the trunk, but no dorsal or ventral processes 

 and no cephalic barbs. Urosome small, 2-segmented ; no caudal rami. 

 First antennae fleshy, usually 2-segmented, the distal segment a small 

 knob armed with short spines; second antennae stout curved claws; 

 mandible falcate, toothed on both margins ; maxilla spinif orm, with 

 or without a palp ; two pairs of uniramose cylindrical legs, usually 

 bilobed at their tips ; sometimes biramose, rami rudimentary. 



Male. — Head fused with the first two thoracic segments and bear- 

 ing all the appendages except the caudal rami; trunk 4-segmented, 

 anal segment very thick; caudal rami short, spinif orm. The two 

 pairs of antennae at the extreme anterior margin of the head are 

 dorsal rather than terminal ; first pair indistinctly segmented, second 

 pair with a stout apical claw; mouth parts as in the female; two 

 pairs of uniramose legs, each a 1-segmented lamina with two to four 

 marginal setae. 



Remarks. — This new genus was proposed in 1927 to include all 

 those species of Ghondracanthus that lack dorsal and ventral proc- 

 esses and cephalic barbs. The swimming legs are even more rudi- 

 mentary than in Ghondracanthus., and are often simple 1-segmented 

 laminae without lobes, spines, or setae. In the males the first two 

 thoracic segments are fused with the head, bringing all the appen- 

 dages onto the cephalothorax except the minute caudal rami. The 

 legs also are flattened laminae with marginal setae. 



KETi' TO THE SPECIES (FEMALES) 



1. First 2 thoracic segments mucli wider than head ; posterior proc- 



esses longer that last trunk segment exilipes, new species (p. 501) 



First 2 tlioracic segments much narrower tlian head ; posterior 

 processes much shorter than last trunk segment 2 



2. Head transversely elliptical, wider than long, not narrowed at 



either end; fused fourth and fifth segment definitely longer 



than third 3 



Head much longer than wide, one end conspicuously narrowed ; 



fused fourth and fifth segment longer or shorter than third 4 



