Cope.] [May 6, 1870. 



curves, the less median not completed but interrupted by the margin of 

 the scale. Near the margin all the ridges become gently zig-zagged. 



There is no depression between the two portions of the dorsal fin, though 

 the cartilagius portion is the more elevated. Laid backwards, the latter 

 is in line with the extremity of the anal, and both extend beyond the basis 

 of the caudal. 



The close affinities of this genus are difficult to determine with entire 

 satisfaction. In its smooth cranial bones and united dorsals it is like the 

 genera Apsilus Cuv. Val. of the Atlantic, and Micropterus Lac. of the fresh 

 waters of North America. Its numerous ventral radii, agreeing with 

 those of the BerycidaB (or Agassiz' section Holocentri in Poiss. Fossiles) 

 separate it entirely from the above genera. The absence of the emarigina- 

 tion of the operculum, also distinguishes it from Micropterus. Its affini- 

 ties are, however, entirely remote from the Berycida3. The genus to which 

 it stands in nearest relationship, is PygaBus, of Agassiz, which he refers to 

 the Chaetodontidae, and which, if so referred, will intervene between the 

 typical forms of the family, and the aberrant Toxotes. The only char- 

 acter by which I distinguish it from Pyga3us, is the presence of one or two 

 additional ventral radii, the number in the latter genus being I. 5. Nine 

 species of that genus are described in the Poissons Fossiles all from 

 Monte Bolca, and the existence of the present near ally, suggests a deter- 

 mination of the age of the Green River beds, which the other species do 

 not furnish. This would be upper Eocene. 



ASINEOPS SQUAMIFRONS, Cope, Sp. 11OV. 



General form is sub-oblong, the greatest depth just behind the head, 

 and contained two and a half times in the length exclusive of caudal fin. 

 Radii D. VIII, 14; A. II, 9; C. 14; V.I, 7; P. ?11 ?13. Scales 5 ?30 10, 

 vertical line counted a little behind the ventral fins. The line of the ex- 

 tremities of the second dorsal and anal fins, marks the basal third of the 

 caudal fin. The dorsal spines are sub-cylindric, slightly curved, and of 

 nearly equal length; the length equals the depth of the body at the middle 

 of the second dorsal fin. 



The external series of villiform teeth are stout of their kind, conic, and 

 a little incurved. I cannot see the pharyngeal bones or teeth. 



The number of vertebra which extends between the caudal fin and the 

 superior margin of the operculum, where one or more are concealed, is 

 twenty-five, of which fifteen are of the caudal portion (in two I can only 

 count fourteen). 



The mouth is directed obliquely downwards and is rather large ; the 

 mandible, when closed, does not project beyond the premaxillary border. 

 The maxillary, where preserved, is narrow distally, and does not project 

 beyond the posterior line of the orbit. The latter is rather small, and 

 though not well defined in any specimen, is not more than one-eighth the 

 length of the head, and 1.5 to, 1.75 times inside of muzzle. The margins 

 of all the opercular bones are entire and smooth. The interoperculum is 

 narrow, and lies obliquely upwards, narrowing the operculum. The 



A. P. s. VOL. xi. 20E 



