, 



346 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. Ill 



has the distal extremity expanded to articulate with the short 

 flat bones of the fore-arm ; the carpus or wrist is composed of 

 a double row of from six to eight discoidal ossicula, which 

 support the slender elongated metacarpals, that articulate with 

 the digital or phalangeal bones ; the latter are connected by 

 flattened surfaces. The entire series of bones was, doubtless, 

 enveloped in one common integument, in like manner as the 

 paddles of the cetacea. 



The pelvis, which is well shown in the specimen before us, 

 consists of strong and short iliac, and broad pubic and isckiac 

 bones ; the two latter being expanded in the antero-posterior 

 direction, like the coracoids. 



The hinder paddles are very similar in their construction to 

 the anterior, which they equal in size. 



PHYSIOLOGICAL INFERENCES. Mr. Conybeare concludes his 

 admirable memoir with the following general remarks on the 

 habits and economy of this tribe of marine saurians : 



" In its progression the Plesiosaurus must have more nearly 

 resembled the Turtles than any other reptiles. That it was 

 aquatic is evident from the form of its paddles ; that it was 

 marine is almost equally so from the remains with which its 

 bones are universally associated ; ] that it may have occasionally 

 visited the shore, the resemblance of its extremities to those 

 of the turtle may lead us to conjecture, but its motion 

 must have been very awkward on land : its long neck must 

 have impeded its motion through the water, presenting a 

 striking contrast to the organization which so admirably fits 

 the Ichthyosaurus to cut through the waves. May it not, 

 therefore, be concluded, since, in addition to these circum- 

 stances, its respiration must have required frequent access of 

 air, that it swam upon or near the surface, arching its long 

 neck like the swan, and occasionally darting it down at the 

 fish which happened to float within its reach? It may, 

 perhaps, have lurked in shoal water along the coast, concealed 

 among the sea- weed, and raising its nostrils to a level with the 

 surface from a considerable depth, may have found a secure 

 retreat from the assaults of its enemies ; while the length and 

 flexibility of its neck may have compensated for the want of 

 strength in its jaws, and its incapacity for swift motion through 



1 Remains of Plesiosauri have since been discovered in the Wealden 

 formation. See " Fossils of Tilgate Forest," PI. IX. 



