﻿CATALOGUE 



OF 



FOSSIL FISHES 



PART II. 



Subclass I. ELASMOBRANCHII (continued). 

 Order III. ACANTHODII. 



Notochord persistent ; endoskeletal cartilage superficially calcified, 

 often granulated. Cranial roof covered with irregular small dermal 

 elements, and orbit frequently surrounded by circumorbitaljplates ; 

 teeth, when present, firmly fixed to membrane-bones upon the 

 pterygoquadrate and mandibular cartilages. Gill-arches each with 

 a close series of prominent dermal appendages, probably supports 

 for a cutaneous flap. Endoskeletal cartilages of all the fins much 

 abbreviated, and the dermal expansion almost or completely desti- 

 tute of rays ; each of the paired fins and most of the median fins 

 provided with an anterior spine ; no claspers in the male. Tail 

 heterocercal. Dermal armature of trunk consisting of small, closely 

 arranged, quadrate granules, which also extend over the greater 

 portion of the fins ; lateral line passing between two series of the 

 granules. 



Synopsis of Families. 



A. One dorsal fin. 



Clavicular bones absent Acanthodid^e (p. 2). 



B. Two dorsal fins. 



Clavicular bones absent Ischnacanthidje (p. 20). 



Clavicular bones present Diplacantbtd^ (p. 22). 



PART II. B 



