﻿PLATYSOUATIDiE. 541 



Cheirodopsis geikiei, Traquair. 



1881. Cheirodopsis geikiei, II. H. Traquair, Trans. Eoy. Soc. Edinb. 



vol. xxx. p. 56, pi. v. figs. 17-19. 

 1890. Cheirodopsis geikiei, R. IT. Traquair, Ann. Mag. Nat. Hist. [6] 



vol. vi. p. 494. 



Type. Imperfect fish, wanting paired and caudal fins ; Geol. 

 Survey of Scotland, Edinburgh. 



The type species, of small size. Head relatively large, it with 

 the opercular apparatus probably measuring more than one quarter 

 of the total length of the fish ; external bones ornamented with 

 coarse, tortuous, and reticulating corrugations. Scales with an 

 especially coarse ornament. 



This species cannot be satisfactorily defined until the discovery 

 of more completely preserved specimens. 



Form. Sf Loc. Calciferous Sandstones (Cement-stone Group) : 

 Eskdale, Dumfriesshire. 



P. 4056. Remains of two small fishes, one showing parts of the 

 median fins. Purchased, 1883. 



P. 4084. Imperfect large specimen, wanting the tail and the greater 

 portion of the head, and with fragments only of the 

 dorsal and anal fins. The length of the trunk from the 

 pectoral areh to the end of the caudal pedicle must have 

 been originally about 0*06. Purchased, 1883. 



Genus PLATYSOMUS, Agassiz. 



[Poiss. Foss. vol. ii. pt. i. 1835, pp. 6, 161.] 



Syn. JJropteryx, L. Agassiz, MS. in collections. 



Trunk deep, more or less rhombic, the dorsal and ventral margin 

 being angulated or sharply rounded. Eacial contour of head steep, 

 with no marked prominence above or in advance of the orbits ; 

 margins of jaws with minute styliform teeth, tubercular within. 

 Fin-rays closely articulated and distally bifurcating ; fulcra small 

 or absent. Pectoral fins small, inferiorly placed ; pelvic fins much 

 smaller and remote. Dorsal fin arising about the middle point of 

 the back, much elongated, high and acuminate in front, low and 

 fringe-like in the posterior two- thirds ; anal fin similar in form, 

 somewhat shorter, but terminating at the same point posteriorly ; 

 caudal fin deeply cleft, nearly equilobate. Scales ornamented with 

 more or less vertical striations, with smooth hinder border, and 

 narrow overlapped anterior border ; principal flank-scales very deep 



