552 ICTHYOSAURUS. 



tail ; whilst the spinal column could not have been sufficiently 

 strong to support the weight of the trunk upon land. But the 

 progression of these animals through the water was accomplished 

 in part by means of the anterior and posterior extremities, which 



FIG. 320. ICHTHYOSAURUS. 



are very efficient instruments of propulsion, being formed very 

 much upon the plan of the paddles of the Whale; but the 

 number of fingers and phalanges was much greater; and the 

 bones themselves, being shorter, were arranged in a tessellated 

 manner. The muzzle is elongated and pointed ; and the teeth 

 very numerous. The general form of the head is not unlike that 

 of the Porpoise ; but it must have had far greater strength, and 

 the surface for the attachment of muscles is very extensive. The 

 form and solidity of the sternal arch, to which the anterior pad- 

 dles are attached, show that provision was made for imparting 

 enormous power and firmness to these ; and certain peculiarities 

 in the structure of the tail seem to prove, that the Ichthyosaurus 

 must have had a vertical cartilaginous tail-fin, like that which is 

 seen on the back of many Cetacea. From the absence of any 

 remains of scales or plates, it may be concluded that the skin 

 was naked, like that of the Whales and their allies. There is no 

 question that the Ichthyosaurus was exclusively an air-breathing 

 animal; no trace of any adaptation to branchial respiration 

 being perceptible. From the remains of partially-digested food, 

 which are found with their bones, it appears that they fed (as 

 might have been anticipated) exclusively upon Fishes; and 

 especially upon one species, which is known only in a fossil 

 state. Some of the largest of these aquatic Reptiles must have 

 exceeded thirty feet in length ; and it is easily to be conceived 

 that they were very formidable enemies to the other inhabitants 

 of the deep. They seem to have taken the place of the Gram- 



