PTERASPIDiE. 
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. Ventral shield consisting of 
a single convex plate (“ Scaphaspis ”). Caudal region with small 
rhomb 01 dal 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 Jeivisii 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 \ 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 genericallv 
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 view of partially restored fish. 
ventral armature of the animals covered dors ally 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 (Ho. 44116, p. 163). 
1 Quart. Journ. Geol. Soc. vol. xiv. (1858), p. 277. 
2 See especially “ Fishes Old .Red Sandst.” pt. i. (Mon. Paksont. Soc. 1868), 
p. 28. 
3 A. von Alth, “Ueber die Zusammengekorigkeit der den Fischgattungen 
Pteraspis, Cyathaspis, und Scaphaspis zugesekriebenen Schilder ” (Beitr. 
Palaont. Oesterr.-TJngarns, vol. v. 1886), p. 61, pi. xxiv. 
PART II. 
M 
