﻿PHYLL0LEPID2E. 313 



Museum of Natural History. A single species is described as follows, 

 but there are no examples in the Collection : — 



Asterosteus stenoceplialus, J. S. Newberry, Rep. Geol. Surv. Ohio, 

 vol. ii. pt. ii. (1875), p. 36, pi. liv. fig. 1, and Palaeoz. 

 Fishes N. America (Mon. U.S. Geol. Surv. no. xvi. 1889), 

 p. 45, pi. xxx. fig. 1. — Corniferous Limestone (Lower 

 Devonian) ; Sandusky and Delaware, Ohio. [Cranial 

 shield ; Columbia College.] 



Family PHYLLOLEPIDiE. 



An imperfectly definable family, of uncertain position, probably 

 related to the Coccosteidae. Dermal plates very thin, and marked 

 by a superficial ornament of rugae, more or less following the con- 

 centric or radiating lines of growth. 



Synopsis of Genera. 



Superficial rugae concentric .... Phyllolepis (p. 313). 

 Superficial rugae radiating Holonema (p. 314). 



Genus PHYLLOLEPIS, Agassiz. 

 [Poiss. Foss. V. G. R. 1844, p. 67.] 



Dermal plates concentrically marked with more or less irregular 

 and wavy rugae. 



These problematical fossils have hitherto only been found isolated, 

 and are rarely met with unbroken. By most palaeontologists they 

 are associated with the Holoptychian Crossopterygii, while Fritsch 

 has compared them with head-bones of Palaeozoic Dipnoi. We 

 venture, however, to adopt the suggestion of Newberry that the 

 plates are truly referable to some so-called " Placoderm," though 

 we would compare them with Coccosteus and its allies rather than 

 with Pterichthys. 



If the last-named suggestion prove correct, this genus will also 

 include the small dermal plates from the Psammites of Condroz 

 (Upper Devonian), Belgium, named Pentagonolepis Tconincki, M. 

 Lohest, Ann. Soc. Geol. BeJg. vol. xv. (1888), p. 161, pi. xi. 

 figs. 1-8. Moreover, the form of the dermal plates cannot be cited 

 in specific diagnoses until their arrangement and homologies have 

 been determined. 



