EOMESODON. 



55 



typical Pycnodont, witli relatively large frontal bones, a small median supra- 

 occipital plate (socc), a quadrangular parietal {pa.), and a rather large squamosal 

 (sq.), all closely ornamented with rows of granulations. One of the principal 

 vomerine teeth, as already noted by Egerton, is coarsely crimped or tuberculated 

 round the apex of the crown; a larger ovoid splenial tooth is smooth and not 

 indented. The dentary bone bears two chisel-shaped teeth, of which the inner is 

 the larger. Beneath the large triangular preopercnlnm there are two branchi- 

 ostegal rays. In the axial skeleton of the trunk, the stont neural spines of the 

 abdominal region do not reach the dorsal border; while neither neurals nor 

 haenials in the caudal region bear any laminar expansion. In the caudal region, 



Fig. 21.— Eomesodon liassicus (Egerton) ; drawing of type specimen, nat. size. — Lower Lias; probably 

 Barrow-on-Soar, Leicestershire. B. M. no. 19864! pa., parietal ; socc, supraoscipital ; sq., squamosal. 



however, as especially well seen in a smaller specimen (B. M. no. P. 1380, with 

 counterpart in the Worcester Museum), each neural spine beneath the dorsal fin is 

 double, a short straight rod arising from the front of the neural arch, the long- 

 neural spine proper arising behind and carving sharply backwards. The number 

 of rays in the dorsal and anal fins seems to have been smaller than in the typical 

 Mesodon. The large dorsal ridge-scales in the anterior part of the eminence are 

 much deepened and modified, but they bear the usual median row of small hooked 

 denticles, of which those in front are inclined backwards, while those behind the 

 eminence seem to be upright or inclined forwards. The ventral ridge-scales are 

 not seen in the type specimen ; but three or four immediately in front of the anal 

 fin in the smaller specimen already mentioned appear to be merely pointed and 

 imbricating, without denticles. The lateral line is well marked by a ridge, and the 



