380 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. IV. 



pressed. The teeth are relatively large, round, conical, and 

 longitudinally furrowed, the base being expanded and deeply 

 grooved ; there are from 40 to 50 on each side the upper, and 

 from 25 to 30 on each ramus of the lower jaw. 



The anterior paddles are three times longer than the poste- 

 rior pair, and are proportionately broader, and contain a greater 

 number of ossicles, than in other species. This character 

 induced Mr. Hawkins to change the specific name to chiro- 

 polyostinus, (or many-boned paddle. 1 ) There are eight meta- 

 carpal bones, and two hundred and twelve digital ossicles. 

 The huuierus is relatively shorter and stouter than in any 

 other species. 



Professor Owen considers that each anterior paddle of 

 this species has an additional series of digits, and about 50 

 more phalangeal bones, than that of the Ich. intermedius, the 

 entire breadth and the power of the anterior fins being thereby 

 increased. 



There are 17 sclerotic plates in each eye ; the orbit and eye 

 are relatively smaller than in Ich. tenuirostris. 



This is one of the larger species of the genus, some speci- 

 mens indicating a total length of 14 feet. 



The specimen in Case A, which is figured by Mr. Hawkins 

 in PL VII. shows the fractured or dislocated state of the tail, at 

 about one-fourth of the length from its distal extremity, which 

 Professor Owen supposes is connected with the presence of a 

 large tegumentary caudal fin : and the laterally compressed 

 form of the terminal caudal vertebra, first ascertained by Sir 

 Philip Grey Egerton, is presumed to afford additional demon- 

 stration of the existence and direction of such an organ. 2 



ANGLE BETWEEN WALL-CASES A & B. 

 Part of the series of bones of a paddle of Ichthyosaurus platyodon. 



Portion of an enormous cranium of Ichthyos. platyodon. | Hawkins, PI. VIII. 



Magnificent cranium and jaws, and part of the spine of Ichthyos. platyodon. 



Various specimens of paddle bones, &c. 



ICHTHYOSAURUS PLATYODON S (Conybeare). Wall-cases B and 



1 Hawkins's " Memoir," p. 25, PI. VII. X. 



2 See " Brit. Assoc. Reports," p. 87. 



3 Ibid. 1839, p. 112. 



