460 GEOLOGICAL SUEVEY OF THE TEERITOEIES. 



pectoral spine is rather small, and bears a row of recurved hooks on its 

 posterior face ; there are none on the anterior face. 



The head is broad, short, and rounded in front, which, with the unci- 

 nate character of the serration of the pectoral spine, reminds one of the 

 existing genus Noturus. As compared with the five species of Bhine- 

 astes described from the Bridger Eocene, the present species is distin- 

 guished by the small size and uncini of the pectoral spine. 



Measurements. 



M. 



Lengtli of head to clavicle, (below) 0.018 



Width of head, (below) 036 



Width of scapular arch, (below) Oil 



Expanse modified diapophyses 020 



Length of modified vertebrse 0115 



Length of pectoral spine 0^1 



From the Tertiary shale of the South Park, Colorado. 



AMYZOIs^, Cope. 



Hayden's Annual Report, 1872, p. 642. 



Amyzon commune. Cope, Bullet. U. S. Geol. Survey, No. 2, 1874, p. 50. 



In describing this species, the following additions to our knowledge of 

 the generic characters may be made. Tbere is an oi:)en fr on to-parietal 

 fontanelle ; the premaxillary forms the entire superior arch of the mouth; 

 the pharyngeal bones are expanded behind ; there are 12-13 rays of the 

 ventral iin ; there is a lateral line of pores, which divides the scales it 

 pierces to the margin. 



The greatest depth of the body is just anterior to the dorsal fin, and 

 enters the length 2.66 times to the base of the caudal fin, or a little 

 more than three times, including the caudal fin. The length of the head 

 enters the former distance a little over 3.25 times. The general form is 

 thus stout and the head shbrt; the front is gently convex and the mouth 

 terminal. There are fifteen or sixteen rows of scales between the bases 

 of the dorsal and ventral, fins. They are marked by close concentric 

 lines, which are interrupted by the radii, of which eight to fifteen cross 

 them on the exposed surface, forming an elegant pattern. At the center 

 of the scale, the interrupted lines inclose an areolation. The extended 

 pectoral fin reaches the ventral, or nearly so ; the latter originates be- 

 neath the anterior rays of the dorsal, or in some specimens a litttle be- 

 hind 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 is a little nearer the basis of the caudal fin 

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

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

 Eadii, D,, 33; P., 14; V., 13; A., 12. The caudal is strongly emarginate, 

 and displays equal lobes. 



Measurements. 



M. 



Length of a large specimen, (10.25 inches) 0.250 



Length of a medium specimen 182 



Depth at occiput - 043 



Depth at dorsal fin 057 



Depth at caudal peduncle ^ 023 



Length of head, axialx 044 



Lengthi to D. 1, axial 075 



Length to end of dorsal, axial 131 



Length to basis of .caudal fin 146 



Length of basis of anal tin 023 



