792 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



a Protoponts, is at least specifically distinct. My specimens are, however, 

 neither adult nor in good condition, and I prefer to leave the task of 

 describing a new species to some later observer. 



Family HYODONTID^. 



Genus HYODON Le Sueur. 



i 



11. — Hyodon (Elattonistius) chrysopsis Rich. 



Gold Eye. Northern Moon- eye. "Kaccaysh." 



1823— Hyodon clodalus EiCH., Franklin's Journal, 716. (Not of Le Sueur.) 

 1836 — Hyodon chrysopsis RiCH.j Fauna Bor.-Am. iii, 532. 



Hyodon chrysopsis DeKay, New York Fauna, Fishes, 1842, 267. 



Hyodon chrysopsis Stoker, Synopsis Fishes N. A. 1846, 463. 



Hyodon chrysopsis Jordan, Bull. U. S. Nat. Mus. x, 67, 1878. 



Hyodon chrysopsis Jordan, Man. Vert. ed. 2d, 277, 1878. 



Hyodon chrysopsis Jordan, Bull. Hayden's Geol. Surv. Terr, iv, 429. 



This beautiful species was first described by Eichardson from speci- 

 mens obtained in the Saskatchawan region. For a time after Richard- 

 son's day the species was kept alive by compilers, but for the last twenty- 

 five years it has been generally ignored or considered a mere synonym 

 of Hyodon tergisus. For its rediscovery science is indebted to the col- 

 lection now under consideration. Its resemblance to H. tergisus is not 

 very great; the body is very much more compressed than in the latter 

 species, the abdomen being almost cultrate, while the dorsal fin is reduced 

 in size, having only about nine developed rays. In view of these pecu- 

 liarities, Dr. Gill and myself have proposed for it the subgeneric name of 

 Elattonistius. At present, Elattonistius is considered as a subgenus of 

 Hyodon, but if no intermediate forms occur it may require elevation to 

 full generic rank. The following analysis of the species of Hyodon gives 

 the principal distinctive characters of tbe three species now known: 

 Elattonistius chrysti;psis, Hyodon tergisus Le S., and Hyodon selenops Jor- 

 dan & Bean. 



*. Dorsal fin reduced, and with only about nine fully developed rays ; abdomen sharply 

 cariuated (Elattonistius): 

 t. Dorsal fin very small, of about nine developed rays (besides the two or three rudi- 

 ments), the length of its longest rays half greater than the length of the base of 

 the fin ; body deep, closely compressed, the belly strongly cariuated both before 

 and behind ventrals; eye moderate (about 3^ in head); scales rather closely im- 

 bricated, 5-r)8-8; pectoral fins falcate, nearly as long as the head, nearly or quite 

 reaching ventrals ; anal with 30 or 31 developed rays ; head 4J- in length ; depth 

 oj chrysopsis. 



**. Dorsal fin moderate and with eleven or twelve fully developed rays; abdomen 

 more or less obtuse (Hyodon) : 

 t. Dorsal fin larger, of about 12 developed rays ; its longest rays scarcely longer than 

 the base of the fin; form of body intermediate; the belly in front of ventrals 

 obtusely cariuated ; eye large, about 3 in head ; scales medium, 5-58-8 ; pectoral 

 fins decidedly shorter than head, not reaching nearly to ventrals ; anal rays 28 

 or 29; head 4-J- in length, the depth about 3 tergisus. 



