174 



AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



This species is inadequately known, having been described from exceed- 

 ingly fragmentary material. The scales agree most nearly, in size and orna- 

 mentation, with those of Platysomus and the species may provisionally be left 

 in that genus. In Benedenius the scales are not nearly so deep. In the few 

 scales in which the external ornamented layer is preserved, it is seen that the 

 ornament agrees well with that of Platysomus, consisting of very fine, parallel, 

 slightly undulating lines, crossing the scale at a slight angle to its vertical 

 axis (plate 30, fig. 7). The flank scales have a depth of about three times 

 their width. Cope's original description may here be quoted. 



Original description 0/ species: "The scale-series tend slightly backward 

 from the vertical below, without distinct curvature. The scales on the 

 sides in front are about five times as deep as long, and they graduate in size 



Fig. 56. — Platysomus ptdmaris Cope. 



A. Imperfect fish in a nodule, natural size. No. 7935 Am. Mus. Texas. 



B. Scales, natural size. One of the fragments representing the type specimen. No. 7281 



Am. Mus. Texas. 



to the lowest undivided row, where they are about twice as deep as long. 

 The small scales of the inferior row are twice as deep as long, and their 

 depth is about half that of the scales of the next series above them. The 

 sculpture of the scales consists of narrow vertical ridges, which are curved 

 slightly backwards below. About ten may be counted, crossing a trans- 

 verse bone on each scale. Each of the narrow scales of the inferior row 

 possesses a median angular keel which extends from the anterior edge 

 downwards and backwards, but which does not reach the posterior edge of 

 the scale. The external face of the clavicle is vertically striate like the 

 scales, and horizontally striate on the recurved portion. The interclavicle 

 has more distinct longitudinal ridges, and one ridge on each side of the 

 low median keel is broken up into enamel tubercles. 



"The body is acute below. This is always the case, whether the frag- 

 ments are compressed or not. 



"Measurements. 



" Diameters of anterior median scale : mm 



Anteroposterior 2 



Vertical 10 



Diameters of lowest normal scale: 



Anteroposterior 3 



Vertical 4 



Depth of scale of inferior border (specimen No. 2) 2.5 



Length of interclavicle (specimen No. 3) 10 



Width of interclavicle in front (No. 3) 8 



Diameter of interclavicular tube, transverse (No. 3) 7" 



