FOSSIL REPTILES OF DORSET. 19 



ICHTHYOSAURUS PLATYODON, Conybeare. 



The skull of this gigantic species far exceeds the two preceding, 

 differing from both in its elliptic orbit. The crowns of the 

 teeth are smooth, enamelled, compressed laterally, sharp-edged and 

 pointed ; there are forty-five in the upper-jaw and forty in the 

 lower ; paddles long and narrow, the fore and hind nearly of equal 

 size ; length from head to tail thirty feet. Lower Lias, Lyme Regis. 

 ICHTHYOSAURUS BREVICEPS, Owen. 



Ichthyosaurus breviceps is characterised by the skull being 

 about one-sixth the length of the body and equally divided between 

 the pre-orbital and post-orbital regions, the fore-paddle twice as long 

 as the hind, the base of the teeth swollen, less compressed than 

 the preceding and more finely grooved ; number of vertebrae one 

 hundred and fifty. From the thick limestone called Broadledge, 

 Lower Lias, Lyme Regis. 



ICHYTHOSAURUS LONCHIODON, OlVen. 



One of the largest of the family, surpassed only by Ich. 

 platyodon ; the head is relatively smaller, the teeth straight and 

 more slender in proportion to length, the crowns round and not 

 compressed, the jaws deeper, tapering less gradually towards the 

 snout. From the Lower Lias of Lyme Regis. 



ICHTHYOSAURUS LATIFRONS, Kon. 



Only the posterior portion of the jaw of this species has been 

 recovered, but sufficient to come to the conclusion that it was long 

 and slender, as also were the teeth ; the fore-paddles are large and 

 strong, the phalanges few and relatively large. From the Lower 

 Lias of Lyme Regis. 



ICHTHYOSAURUS TENUIROSTRIS, Conybeare. 



Characterised by the slenderness and length of the jaw, and by 

 the slenderness of the teeth in proportion to their length, of which 

 there are sixty-five or seventy on each side of the upper jaw and 

 sixty in the lower, directed obliquely backwards; the orbits are 

 very large, which with its flattened cranium gives it a snipe-like 

 appearance. The fore-paddle is as disproportionate to the hind 

 as those of Ich. communis and Ich. intermedium. It has an 



