﻿CXELACANTHID^:. 



395 



The cranium of Macropoma, which may be regarded as a 

 typical Ccelacanth, is well ossified and provided with robust mem- 

 brane-bones. The roof of the skull is divisible " into two moieties, 

 an anterior or frontal, and a posterior or occipito-parietal, which 

 meet at an obtuse angle, the occipito-parietal moiety being nearly 

 parallel with the base of the skull, while the frontal slopes obliquely 

 forwards and downwards to the snout ; the occipito-parietal portion 

 is slightly convex from before backwards, and more so from side to 

 side ; while the frontal portion, though convex from side to side, is 

 slightly concave from before backwaids." The occipito-parietal 

 region comprises a pair of large bones meeting in the middle line, 

 evidently to be regarded as parietals, flanked postero-externally by 

 a pair of triangular bones, which appear to represent the squamosal 

 fused with the post-temporal. The frontals are long and narrow, 

 separated by a suture at the median line, and flanked on each outer 

 margin by a single series of small quadrate membrane-bones, which 

 have been named parafrontals. The chondrocranium itself is exten- 

 sively ossified, but there is no interorbital septum ; and the base is 

 formed by a long slender parasphenoid bone, which exhibits a spatu- 

 late expansion anteriorly. 



The hyomandibular and pterygo-quadrate arcade are fused into 

 a continuous triangular, lamelliform bone on each side, articulating 

 with the hinder portion of the cranium above, and provided postero- 

 inferiorly with a ginglymoid condyle for the articulation of the 

 mandible below. The bone terminates in an attenuated angle in 

 front, and its superior portion is inclined inwards, so that the inner 

 surface forms the roof of the mouth ; this surface is finely granu- 

 lated and its lower border exhibits weJl-developed teeth, while the 

 outer surface is smooth. In front of the pterygo-quadrates, a pair 

 of thin small palatine bones, with more or less formidable teeth, 

 occurs ; and immediately in advance of these is a large azygous 

 robust element, beaiing a cluster of strong teeth, probably to be 

 regarded as the coalesced vomers. The actual termination of the 

 snout is not definitely known in Macropoma • but in the Upper 

 Jurassic genera it is stated by von Zittel l to consist of a blunt 

 rostrum, showing no sutures, and much resembling that of some 

 of the early Dipnoi. The eye is surrounded by a ring of small, 

 delicate sclerotic plates, suggestive of those of certain Palaeozoic 

 Amphibia. There are two large quadrate cheek-plates, one above the 



1 Handb. Palaeont. vol. iii. p. 173. This description suggests that the 

 undetermined snout from the Sussex Chalk noticed and figured by the present 

 writer in Proc. Geol. Assoc, vol. xi. (1889), p. 31, pi. i, fig. 6, may pertain to 

 Macropoma. 



