﻿COCCOSTEID^. 277 



Family COCCOSTEIDiE. 



Cranial shield consisting of few elements : — a median occipital, 

 with two pairs of bones following immediately in front, this series 

 being terminated by an anterior azygous element over the ethmoidal 

 region ; three lateral pairs of bones forming the sides of the shield. 

 Narial openings small and anteriorly situated. Maxilla and pre- 

 maxilla well developed, but toothless ; dentition, when present, con- 

 sisting of conical teeth fused with the oral margin of the mandible 

 and with two inner pairs of bones in the upper jaw (presumably 

 palatine and vomerine). Abdominal region with a dorsal and ventral 

 armature, the large dorsal plate having a deep inner longitudinal 

 keel, evidently for connection with the neural arches of the endo- 

 skeletal axis. 



Synopsis of Genera. 



I. Orbits forming notches in the cranial 



shield. 



A. No pineal foramen. 



Median bone over pineal region ; no 



pectoral spine Coccosteus (p. 278). 



Similar, but with pectoral spine .... Brachydirus (p. 294). 

 No median bone over pineal region ; 



no pectoral spine Phlyctcsnaspis (p. 295). 



B. Pineal foramen present. 



Scutes ornamented with fused series 



of tubercles Chelyophorus (p. 299). 



Scutes smooth or faintly rugose ; 



teeth prominent Dinichthys (p. 300). 



Scutes smooth or faintly rugose ; no 



teeth in mandible Titanichthys (p. 302). 



II. Orbits completely enclosed in the cranial 



shield. 



Scutes finely and closely tubercu- 



lated ; cranial shield much arched. Macropetalichthys (p. 303), 



Scutes finely and closely tubercu- 

 lated ; cranial shield nearly flat ; 

 antero-lateral processes of abdomi- 

 nal shield small Homosteus (p. 304). 



Scutes coarsely and sparsely tuber- 

 culated ; cranial shield nearly flat ; 

 antero-lateral processes of abdomi- 

 nal shield enormous Heterostev.s (p. 308). 



