750 THE AMYZON BEDS. 



ventral fins. They are marked by close concentric lines, which are inter- 

 rupted by the radii, of which eight to fifteen cross them on the exposed sur- 

 face, forming an elegant pattern. At the center of the scale the interrupted 

 lines inclose an areolation. The extended j^ectoral fin reaches the ventral, 

 or nearly so; the latter originates beneath the anterior rays of the dorsal, 

 or in some species a little behind that point. They do not reach the anal 

 when appressed. The anal is rather short, and has long anterior radii. 

 The dorsal is elevated in front, the first ray a little nearer the basis of the 

 caudal fin than the end of muzzle. Its median and posterior rays are much 

 shortened; the latter are continued to near the base of the anal fin. Radii 

 D. 33; P. 14; V. 13; A. 12. The caudal is strongly emarginate and dis- 

 plays equal lobes. 



Measurements. 



M. 



Leiigth of a large specimen (10.25 inches) 0.250 



Length of medium specimen 182 



Depth at occiput of do 043 



Depth at dorsal fin 057 



Depth caudiil peduncle 023 



Length of head (axial) 044 



Length to D. 1 (axial) 075 



Length to end of dorsal (axial) 131 



Length to hasis of caudal fin 146 



Length of hasis of anal fin 023 



There are thirty-eight or thirty-nine vertebrae, of which nine are ante- 

 rior to the first interneural spine, and fourteen between that point and the 

 first caudal vertebra. 



A very large number of specimens was obtained by Dr. Hayden and 

 myself from the Tertiary shales of the Middle and South Parks, Colorado. 

 They display but insignificant variations in all respects, and furnish a good 

 basis of determination. They all diff'er from the A. mentale Cope, in the 

 larger numbers of vertebrae and dorsal and anal fin radii, and greater pro- 

 longation of the dorsal fin. 



Amyzon pandatum Cope. 



Bulletin U. S. Geol. Survey Terrs., 2d series, 1875, p. 4. 



Form very stout ; the body deeper in relation to its length than in the 

 known species of Amyzon; greatest depth just in front of dorsal fin, and two- 

 fifths the length to basis of caudal. Length of head one-third the latter. 

 Spines of premaxillaiy causing a j^rotuberance above the end of the muzzle, 

 as in many existing Catostomi. Mouth slightly inferior ; end of muzzle 



