﻿PLATYSOMATTDJS. 



547 



A small species attaining a maximum length of about 012. 

 Greatest depth of trunk exceeding its length from the pectoral arch 

 to the base of the caudal fin ; dorsal margin much raised and angu- 

 lated at a very short distance behind the head ; ventral margin 

 sharply bent, but rounded, immediately behind its middle point. 

 Head relatively large, it with the opercular apparatus and pectoral 

 arch occupying considerably more than one-third of the total length 

 of the fish to the base of the caudal iin ; most of the head-bones 

 finely striated, but those of the cranial roof also in part granulated. 

 Pelvic fins very small, remote ; dorsal fin arising at a point about 

 as far behind the dorsal peak as the distance of the latter from the 

 occiput, terminating some distance in advance of the caudal fin ; 

 anal fin somewhat shorter than the dorsal, but terminating at the 

 same point, and both these fins sharply acuminate in front ; caudal 

 pedicle long and slender, and the width of the caudal fin at the 

 extremity equalling about half the maximum depth of the trunk ; 

 rays of median fins finely ornamented with oblique striae. Scales 

 finely striated, the striae being parallel, even, and regular, vertical 

 on the deeper flank-scales, but oblique on those situated dorsally, 

 ventrally, and upon the caudal region ; ridge-scales in advance of 

 dorsal and anal fins with irregularly arranged, recurved denticles, 

 those of the dorsal margin of the caudal lobe relatively large and 

 granulated. 



Form. Sf Loo. Coal-Measures : Staffordshire, Lancashire, York- 

 shire, and Northumberland ; Midlothian and Lanarkshire. 



P. 237. Much crushed imperfect small specimen, displaying some 

 of the asperities upon the ventral ridge-scales ; Knowles 

 Ironstone Shale, Fenton, North Staffordshire . 



Weaver-Jones Coll. 



P. 1602-3. Three more typical specimens of larger size ; Fenton. 

 One of the two specimens included under the first number 

 shows the distant articulations of the pectoral fin-rays, 

 and the numerous spines upon the dorsal and ventral 

 ridge-scales ; while both this and the third fossil exhibit 

 the ornamentation of the median fin-rays. Egerton Coll. 



P. 3499 a. A very small fish exhibiting the dorsal peak and the greater 

 part of the caudal fin ; also a much crushed larger speci- 

 men, wanting the median fins ; Fenton. The latter 

 specimen shows a' series of mandibular teeth, and one of 

 the pectoral fins with its sparsely jointed rays, which bi- 

 furcate distally : below the anal region of this fish there 



2n2 



