220 



ME. G. A. FROST ON THE INTERNAL 



[June i 9 13, 



the semicostatus zone, where I have found other remains of Ganoids. 

 Close to this is the ' saurian bed/ where I got at about the same 

 time an Ichthyosaurus tetiuirostris, which in life was probably some 

 7 feet long, the body of which was enclosed in a large ovoid 

 nodule of formation similar to the smaller one containing the 

 head of the Dapedius. As we know, from the undigested scales 

 found in the coprolites of the saurians which occur here, that the 

 Ganoid fishes formed the bulk of their food, the juxtaposition of 

 the two is what might be expected. 



Being highly pyritized, the delicate interorbital septum of the 



Dapedius is perfectly pre- 

 Fig. 2. — Cranium of Dapedius 

 granulatus. Natural size. 



supraoceipital 



opistliotic 



post -frontal 



served, and the internal 

 foramina admit of accurate 

 delineation. 



As already noted by 

 Dr. Smith Woodward, the 

 exterior of the skull of 

 Dapedius is entirely ossi- 

 fied, the frontals, parietals, 

 and squamosals almost 

 completely covering the 

 cranium. The frontals 

 show a radiated structure 

 with a bold irregular 

 suture, some ornamenta- 

 tion being apparent to- 

 wards the anterior edges. 



The entire build of the 

 skull is massive, and emi- 

 nently adapted for a stren- 

 uous existence in the 

 Liassic seas ; the heavy 

 outer cartilage-bones are 

 ossified throughout, and, 

 while defended on the 

 outside by the armoured 

 membrane-bones, receive 

 support internally from 

 the arched orbitosphenoids, the whole combining to form such a 

 covering for the brain as to offer the greatest resistance to attack. 



The supra-occipital, which was visible on the exterior of the nodule 

 when found, alone exhibits signs of erosion, exposing very clearly 

 the formation of the bone-cells. The parasphenoid and vomer are 

 confluent, and form a strong deeply-ridged bone, the fore part 

 having a lateral wing for the attachment of the palatines ; the 

 vomer also shows evidences of having borne teeth. 



In Lepjidotus there is a foramen in front of the basipterygoid 

 processes, but this is absent in Dapedius. In front of these 

 processes the parasphenoid is bent sharply upwards, as already 

 mentioned by Dr. A. S. Woodward. This inclination of the para- 



nasaLfossa 



