﻿540 



ACriSTOPTERYGlT. 



Type, Imperfect fish ; Newcastle-upon-Tyne Museum. 



A very small species, with the trunk much deeper than long. 

 Dorsal and ventral scales gran dated, those of the middle of the 

 flank having the tubercles fused into delicate vertical striations. 



Form. $ Loc. Coal-Measures : Northumberland. 



41631. Small pterygoid bone ; Newsham, near Newcastle-upon- 

 Tyne. Presented by T. P. Barkas, Esq., 1869. 



P. 4796. Similar but smaller bone ; Newsham. 



Presented by Sir Richard Owen, K.C.B., 1884. 



The pterygoid or splenial bone of an undetermined species of 

 Cheirodus has also been recorded from the Upper Carboniferous 

 Limestone of Richmond, Yorkshire, by W. J. Barkas, Geol. Mag. 

 [2] vol. i. (1874), p. 431; and a similar fossil from the Toredale 

 Rocks of Wensleydale, Yorkshire, now in the York Museum, is the 

 tj'pe of the genus and species, Hemicladodus unicuspidatus, J. "W. 

 Davis, Quart. Journ. Geol. Soc. vol. xl. (1884), p. 620, pi. xxvii. 

 fig. 24. 



A tooth from the Coal-Measures of Ohio is briefly noticed under 

 the name of Cheirodus acutus, J. S. Newberry, Proc. Acad. Nat. Sci. 

 Philad.vol. viii. (1856), p. 99. 



Scales from the Carboniferous Limestone of Abden, Fifeshire, now 

 in the Edinburgh Museum, are also noticed under the name of 

 Cheirodus crass us, R. H. Traquair, Proc. Roy. Soc. Edinb. vol. xvii. 

 (1890), p. 400. Similar scales are recorded from Beith, Ayrshire. 



Genus CHEIRODOPSIS, Traquair. 



[Trans. Roy. Soc. Edinb. vol. xxx. 1881, p. 56.] 



Trunk deep, the dorsal and ventral margins gently convex. 

 Head and dentition as in Cheirodus. Pectoral and pelvic fins small. 

 Rays of median fins with distant articulations and distally bifur- 

 cating ; fulcra present. Dorsal fin arising considerably behind the 

 middle point of the back, high and acuminate in front, elongated ; 

 anal fin similar, but smaller, opposed to the hinder portion of the 

 dorsal ; caudal fin cleft. Scales very deep and narrow, with re- 

 latively broad overlapped anterior border, and the exposed portion 

 ornamented with a coarse " tuberculo-corrugate " pattern, which 

 passes into prominent serrations at the hinder border ; anterior inner 

 keel thick, and peg-and-socket articulation well developed. 



