181 



Syll^emus latifrons, Cope. 



Represented by the entire head and body of a fish as far as the basis 

 of the ventral fins, excepting the end of the muzzle. The scales are com- 

 pletely preserved, while only the bases of the fins remain. 



The body is subcylindric, while the head is broad and flat above. The 

 inferior side of the head is contracted ; the coracoids forming a keel, and the 

 lower borders of the denlary bones being in contact. The angular portion 

 of the dentary is strongly grooved on its inferior surface, and the proximal or 

 anterior parts of the operculum display a radiate sculpture. The top of the 

 head is smooth, excepting a slight radiate sculpture of the parietals. The 

 outline of the parietals is subround, and a little more extended than that of 

 the supraoccipital, which is a short longitudinal oval. 



There are twenty-six or twenty-seven longitudinal rows of scales, or 

 thirteen on each half; those of the abdomen not differing from those of the 

 sides. The lateral line runs along the eighth below the dorsal fin, originating 

 just above the base of the pectoral fin. There are nine rows of scales between 

 the occiput and the first dorsal ray. I count the bases of fifteen dorsal radii, 

 which are all fissured anteriorly, excepting the first, which is rudimental. 

 The anterior rays are stouter than the posterior, and they embrace the pos- 

 terior part of the ray in front of them by the basal fissure. The posterior 

 rays are much narrowed, and embrace but little. The pectoral rays are 

 nnmerous. The physiognomy of this fish is rendered peculiar by the depressed 

 form of the snout, with the narrow under jaw. It is impossible to be sure 

 whether the muzzle was elongate or not. 



Measurements. 



M. 



Length of the specimen to tbc base of the ventral flu 0. £05 



Length of the specimen to the base of the dorsal 0. 090 



Length of the specimen to tho base of the pectoral 0. 075 



Length of the specimen to the edge of the operculum 0. 071 



Length of the specimen to the edge of the preoperculum 0. 055 



Length of the specimen to the condyle of the mesopterygoid 0. 029 



Length cf the specimen to tho orbit 0.017 



Diameter of the front between the orbits 0. 020 



Diameter of the body at the middle of the dorsal fin 0. 045 



Depth of the body at the middle of the dorsal flu 0. 050 



The specimen was found by Lieutenant Marshall, of the Wheeler United 

 States Geographical Survey, "near the summit of Pike's Peak," Colorado. 

 The specimen has the appearance of having been derived from the Cretaceous 



