Devonian Fish-Fauna of Spifcherjen. 3 



filled with fragments of Ptevaspidian shields too imperfect 

 for specific determination. So far as the writer has observed, 

 the superficial ridged ornament upon these fossils does not 

 exhibit any crimping, being quite smooth and as even as in 

 the typical species. 



Order OSTEOSTRACL 

 Family Cephalaspidae. 



A further examination of the supposed evidence of Gepha- 

 laspis from the Lower Devonian of Spitzbergen (Lankcster, 

 op. cit. p. 5, pi. i. fig. 4, pi. ii. fig. 5) suggests doubts as to 

 the determination of the larger fossil, and proves that the 

 smaller specimen represents a new species of Acanthaspis (see 

 p. 4). It is quite possible that the former may be truly refer- 

 able to the same category as the triangular spines of Psammo- 

 steus and Oracanthus ; but more satisfactory specimens are 

 required for the study of the histology of the fossil. 



Order A N T [ A R C H A. 

 Family Acanthaspidse. 



Exoskeleton robust, ornamented with tubereulations of 

 ganoine ; dorsal and ventral shields of trunk firmly united by 

 the lateral plates, the dorsal comparatively simple, the ventral 

 as in Asterolepida?. [Head unknown.] A pair of fixed, 

 spine-like, lateral appendages in the pectoral region, encased 

 in a thick plate or plates. [Caudal region unknown.] 



The recognition of this family seems to be now rendered 

 possible by the discovery of the specimen described below as 

 Acanthaspis decipiens. 



Genus Acanthaspis. 



Head and trunk broad, not much elevated, and the super- 

 ficial tubereulations distinct, often arranged in regular con- 

 centric series. Anterior dorsal armour apparently consisting 

 of a single broad plate, meeting the ventral armour laterally, 

 and in conjunction with this giving rise to a pair of lateral 

 unciform processes, each bearing a simple, backwardly curved, 

 hollow spine-like appendage. 



Of this imperfectly definable genus only a single species 

 [A. armata^') has hitherto been met with in the Cornifcrous 



* J. S. Newbony, Hep. Geol. Surv. Ohio, vol. ii. pt. ii. (1875), p. .37, 

 pi. Iv. tigs. 1-0. 



1* 



