180 



1875. Cope, Proceedings Academy Philadelphia (January). Gar-fishes in 

 Fort Union beds of Milk River. 



In the .present work, the families, genera, and species are more fully 

 defined than has been heretofore practicable. 



'I PERCESOCES. 



SYLLJEMUS, Cope. 



Allied to the Mugilidce. A short spinous dorsal fiu; ventral fins' abdom- 

 inal, posterior to the spinous dorsal. Pectoral fins subinferior in position. 

 Coracoid bones forming a compressed, keeled body. Scales large, cycloid ; 

 lateral line present, extending along the middle of the sides. Parietal bones 

 less than epiotics, entirely separated by the supraoccipital. Frontal bones 

 large, wide, their common suture distinct. 



The opercular apparatus extends obliquely backward, while the man- 

 dible is produced forward. Hence, the inferior part of the hyomandibular 

 and the symplectic are directed obliquely forward. The end of the muzzle 

 is broken off, but the posterior part of the dentary bone does not exhibit any 

 teeth. The opercular bones are thin, and their inferior borders reach the 

 median line of the inferior side of the head. 



The only species of this genus which has fallen under my observation 

 is represented by a specimen in which the body posterior, to the femoral 

 bones is wanting. The surface is covered with scales, so that only the out- 

 lines of the femoral boues can be distinctly seen. These are thickened, and 

 curved outward ; those of opposite sides are well separated from each other. 

 The scales exhibit a very delicate concentric line-sculpture. 



The very posterior position of the ventral fins distinguishes this genus from 

 Mugil, while the inferior position of the pectoral fins is not seen in Atherina, 

 The lateral line does not occupy the inferior position seen in the Scombreso- 

 cidce. As compared with Apsopelix, Cope, from the Benton group of Kansas. 

 Syllccmus differs in the absence of continuous dorsal radii or interneural spines 

 anterior to the ventral fins. There is doubtless some affinity between the two 

 genera, as the other characters are quite similar. I was unable to detect a 

 lateral lino in Apsopelix. It is possible that a catalogue-name of Agassiz, viz, 

 Calamopleurus (Puiss. Foss., V, p. 122), refers to this or some allied genus; 

 but I am unable to discover that it has ever been described. 



