384 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



ICHTHYOSAURUS LONCHIODON.' (Owen.) Wall-case D. A 

 fine skeleton of this species, fifteen feet in length, with the 

 skull and jaws, one anterior and one posterior paddle, is 

 deposited in Wall-case D ; the spinal column, consisting of 

 upwards of 120 vertebrae, remains, but part of the tail is defi- 

 cient. This specimen is from Lyme Regis, and was obtained 

 by Miss Anning. The teeth, as implied by the specific name 

 (lonchiodon, signifying lance-shaped), are more slender in pro- 

 portion to their length than in I. communis, or I. platyodon, 

 and straighter than in I. tenuirostris, or I. intermedius. 

 Their base is cylindrical, and regularly fluted ; the transverse 

 section of the crown is nearly circular, not compressed, as in 

 I. platyodon. The paddle is relatively less than in the last 

 named species. 



But the great interest of this fossil consists in the preserva- 

 tion of the elements of the os hyoides, which are seen in their 

 natural relative position between the rami of the lower jaw ; 

 these parts of the structure of the Ichthyosaurus were first 

 detected by the illustrious Cuvier. 1 



The hyoid bones in the skeleton before us are thus de- 

 scribed by Prof. Owen : 



" The cornua are robust, elongated, sub-prismatic bones, slightly 

 enlarged and truncate at both extremities ; their junction with the small 

 flattened hyoid body seems to have been by means of abundant flexible 

 ligamentous material ; the length of each cornu is a fifth part that of 

 the lower jaw. 



" The condition of the hyoid apparatus in the Ichthyosaurus, besides 

 corroborating the evidence afforded by the rest of the skeleton, 

 that this extinct reptile was an air-breather, indicates that its tongue 

 was almost as little developed as in the Crocodile ; and since the 

 Ichthyosaurus obtained its food at all times under the same circum- 

 stances which necessitate the modification of the hyoid apparatus in 

 the Crocodile, it maybe inferred that the hyoid arch was physiologically 

 related to the working of a similar valvular apparatus for defending 

 the orifice of its air-tube from the water admitted into the interspace 

 of the jaws, during the capture and slaughter of its prey ; and the 

 structure and the relative position of the hyoid apparatus corroborates 

 this inference." 2 



1 " Os. Foss." tome v. p. 465. 



2 " Brit. Assoc. Kep." p. 98. 



