BRITISH FOSSIL REPTILES. 99 



the size and uses of the thick or long, and commonly bifurcate 

 tongue ; while in the Crocodile the hyoid apparatus is reduced 

 to the same number of pieces as in the Ichf/u/osaurns, the 

 body or median plate, however, being cartilaginous, and the 

 two straight cornua relatively smaller. This simple apparatus 

 is far less subservient to the support or movement of the 

 tongue, — which, as Aristotle long ago pointed out, is as little 

 conspicuous in the Crocodile as in many fishes, — than to the 

 mechanism for defending the larynx and pharynx from the 

 entry of water, during the struggles of a submerged prey, when 

 the mouth of the air-breathing destroyer is necessarily exposed 

 to the free ingress of the ambient element. 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 Ichthyo- 

 saurus obtained its food at all tunes under the same circum- 

 stances which necessitate the modification of the hyoid appa- 

 ratus in the Crocodile, it may be 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 cap- 

 ture and slaughter of its prey ; and the structure and relative 

 position of the hyoid apparatus corroborates this inference. 



Vertebral Column. — In the vertebrae of the Ichthyosaurus are 

 observed the centrum, the neurapophyses and their spine, the 

 haemapophyses, and the costal elements. The centrum or ver- 

 tebral body is characterized, as is well known, by its antero-pos- 

 terior compression and the concave form of its articular surfaces, 

 a structure in which the Ichthyosaurus departs from the Crocodi- 

 lian and Lacertian types of Sauria, and resembles the Perenni- 

 branchiate Amphibians and Fishes. The body of an Ichthyosau- 

 rian vertebra might however be distinguished from that of any 

 fish, by the presence of the neurapophyseal pits on each side of 

 the shallow canal for the spinal cord ; for the neurapophyses, 

 though anchylosed above to each other and to their spinous pro- 

 cesses, always remain detached from the centre below. We can- 

 not attach much force to the teleological argument founded upon 

 this structure, or admit its necessity toco-operate with the cupped 

 form of the intervertebral joints in giving flexibility to the ver- 

 tebral column, and assisting its vibratory motions necessary in 

 the mode of progression, which seems to have been common to 

 the Ichthyosaurus and Fishes ; because in all the osseous fishes 

 these parts are consolidated with the vertebral centrum as in the 

 Cetaceans and other Mammals, and yet the vertebral column is 

 not so locked together as to render impossible such motion of its 



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