62 rnOCEEDI^OS of the national museum. vol.53. 



here the neck is a continuation of the trunk in line with the body 

 axis, as in Lernaeenicus. 



This must produce a great difference in the internal anatomy and 

 alone is sufficient to distinguish the genera. The swimming legs are 

 smaller and less developed in the present genus, and only the cepha- 

 lothorax is buried in the bulbus arteriosus of the fish's heart, while 

 in Peroderma the entire body is buried in the lateral muscles of the 

 host, leaving only the egg strings hanging free, and the tubular 

 cephalic processes adhere to the vertebral column. The species may 

 be distinguished as follows : 



EET TO THE SPECIES. 



Egg strings much longer than the body ; soft lateral horns entirely confined to 

 cephalotliorax mcdusaeus (Wilson), 190S, p. 52. 



Eggs strings only a quarter the length of the body ; lamellar wings on the 

 thorax also heUotiii (Richiardi), 1S82, p. 55. 



CARDIODECTES MEDUSAEUS (Wilson). 



Plate 3, figs. 15-23. 



Lernaeenicus mcdusaens Wilson, 1908, p. 458, pi. 76, figs. 99 and 100. — 

 BniAN, 1912, p. 27, pi. 10, figs. 1-5. 



Host and record of specimens. — Two females were obtained from 

 the throat of Nannohrachium leiicopsarum on the Pacific coast at 

 stations 4434 and 4541 by the United States Bureau of Fisheries 

 steamer Albatross in 1904. 



One has received Cat. No. 4778G, U.S.N.M., while the other was 

 sacrificed to obtain the data given below. Both specimens, as also 

 the one obtained in 1908, were fastened to the throat of their host, 

 with the head and frontal processes buried in the bulbus arteriosus 

 of the heart, the body turned back at right angles outside the fish's 

 skin, with the ventral side of the parasite toward its host. Naturally 

 there would be but a single specimen on each fish, since there would 

 be no room for a second parasite's head within the fish's heart. A 

 third specimen was obtained by the Bureau of Fisheries' steamer 

 Albatross at Misaki, Japan, in the throat of Diaphus glanduliferus. 

 As the host is small the two have been preserved together with Cat. 

 No. 47823, U.S.N.M. 



Specific characters of female. — Cephalotliorax ellipsoidal, nearly 

 as wide as long and evenly rounded ; a pair of soft horns extending 

 forward from the anterior margin and a second pair extending out- 

 ward and ventrally from the postero-lateral margin, the bases of 

 the two pairs running together along the sides of the head. The 

 posterior pair are divided into lobes, more or less swollen into 

 spneres, while the anterior pair are strongly flattened dorso-ven- 

 trally, and from them chiefly, but also to some extent from the ante- 



