﻿CERASPIDJE. 233 



Family CERASPID.E. 



An imperfectly definable family, of uncertain position, known 

 only by the detached dermal plates ; these plates consisting of a 

 very thick middle layer of cancellous tissue, an inner squamous 

 layer, and a thin outer layer with a fine superficial ribbed ornament. 



Genus CERASPIS, Schluter. 

 [Sitzungsb. niederrheiu. Ges. Bonn, 1887, p. 120.] 



The type and only known genus. Body deep, with a sharp 

 longitudinal dorsal ridge. 



The structure of the shield suggested to Schliiter the associa- 

 tion of this genus with the Pteraspidse ; but the examination of a 

 large series of specimens in the Museum of Comparative Zoology, 

 Cambridge, Mass., has led the present writer to refer the proble- 

 matical fish to the Antiarcha. One specimen shows two much 

 elevated azygous plates in direct apposition one behind the other, 

 very similar in form and proportions to the median dorsal plates of 

 Pterichthys rhenanus ; the posterior plate, however, is relatively 

 larger, has an especially deep keel, and seems to have been pro- 

 duced into a posterior horn. Another plate is very similar in form 

 to a ventro-lateral of Pterichtliys ; and it may be added that, where 

 thickened, the plates of the Asterolepidae have an inner cancel- 

 lated structure precisely similar to that observed in the fossils now 

 under discussion. 



Ceraspis carinata, Schliiter. 



1887. Ceraspis carinatus, C. Schliiter, Sitzungsb. niederrhein. Ges. 



Bonn, p. 120. 

 1887. Ceraspis hayenensis, C. Schluter, ibid. p. 122. 



Type. Imperfect dermal plates ; University Museum, Bonn. 



The type species, of moderate size. The horn-like process of the 

 hinder dorsal plate {carinatus) much laterally compressed, with 

 smooth, flattened, longitudinal ribs, very closely arranged, some- 

 times intercalated and bifurcating. Anterior median dorsal plate 

 (liagenensis) much longer than broad, with a sharp longitudinal 

 median keel rising to an obtuse apex behind its middle point ; the 

 sides of the plate facetted and marked with fine ridges parallel to 

 the outer border. 



Form. $ Loc. Middle Devonian : Eifel. 



36160. Imperfect large horn-like plate, showing the superficial 

 ribbed ornament above, and the inner cancellated tissue 

 towards its base ; Gerolstein, Purchased. 1861, 



