﻿PTERASPIDJE. 161 



pair of postero-lateral cornua, each pierced with a large [? branchial] 

 foramen. [? Pineal body occupying] a pit on the inferior aspect of 

 the dorsal shield between the orbits. Yentral shield consisting of 

 a single convex plate (" Scaphaspis "). Caudal region with small 

 rhomboidal scales, slightly overlapping, and ornamented with few, 

 delicate, imbricating ridges, parallel to the overlapped anterior 

 margins. 



The generic name Pteraspis was originally applied by Kner to the 

 simpleshields named Cephalaspis hivisii and C. lloydii by Agassiz, 

 in conjunction with similar fossils from Galicia, these being all re- 

 garded as not pertaining to fishes, but most nearly paralleled by the 

 internal shell of the Cephalopod, Sepia. The dermal nature of the 

 specimens and their correct reference to chordate animals was subse- 

 quently determined by Huxley x , who altered the significance of the 

 generic term by regarding as type the complex shield described 

 by Agassiz as Cephalaspis rostratus. Huxley's determination was 

 adopted and extended by Ray Lankester 2 , who published the accom- 

 panying restoration of the dorsal shield (fig. 14), and generically 

 separated the original type species of Kner's Pteraspis under the 

 name of Scaphaspis. The simple shields are now proved to be the 



Fig. 15. 



Pteraspis rostrata (Ag.). — Side Tiew of partially restored fish. 



ventral armature of the animals covered dorsally by the more com- 

 plex shields 3 ; and Scaphaspis thus becomes in part a synonym of 

 Pteraspis, as finally amended. 



The anterior scales of the caudal region are known only in one 

 specimen (No. 44116, p. 163). 



1 Quart. Journ. Geol. Soc. vol. xiv. (1858), p. 277. 



2 See especially " Fishes Old Red Sandst." pt. i. (Mon. Palasont. Soc. 1868), 

 p. 28. 



3 A. von Alth, "Ueber die Zusaramengehorigteit der den Fischgattungen 

 Pteraspis, Cyathaspis, und Scaphaspis zugesohriebenen Schilder" (Beitr. 

 Palaont. Oesterr.-TJngaras, vol. v. 1886), p. 61, pi. xxiv. 



PART n. M 



