216 



EXTINCT ORDERS OF REPTILES. 



short polygonal bones, arranged in generally five longitudinal 

 and closely-approximated rows, the apparent number of the 

 digits being increased by the development of supernumerary 

 rows of " marginal " ossicles on both sides of the paddle. 



Fig. 565. — A, Peetoral arch and foi'e- limbs of Ichthyosaurus : a, Interclaviele ; h, h. 

 Clavicles ; c, c, Scapulae ; d, d, Coracoids ; e, Humerus ; /, Radius ; g. Ulna. (Somewhat 

 altered from Huxley.) b, Pelvis oi Ichthyoscmrus : p, Pubis; il, Ilium ; is, Ischium. 



As regards their distribution in time, the Ichthyosaurs, as 

 before said, are not known with certainty to have existed in 

 rocks earlier than the Lias or later than the Chalk ; and 

 though abundant in the European area, no unequivocal re- 

 mains of the genus have yet been detected in the corre- 

 sponding formations in ISTorth America.^ In the year 1861, 

 however. Professor Marsh discovered in the Coal-measures of 

 Nova Scotia two large amphiccelous vertebrae, which he de- 

 scribed under the name of Eosaitrus Acadknsis. These ver- 

 tebrae (fig. 566) are of very large size (about two and a half 

 inches in diameter), and they are deeply excavated at both 

 ends. They are regarded by Professor Marsh as indicating 



•^ Since these sheets have been in the hands of the printer, Professor Marsh 

 has described the remains of a large Saurian from the Jurassic rocks of the 

 Rocky Mountains, which agrees with Ichthyosaurus in the general structure of 

 the skeleton, but in which there are no teeth. The length of this singular 

 Reptile is about eight or nine feet, the vertebrse are deeply biconcave, there 

 are eight sclerotic plates, and the orbits are very large. It has been named 

 Sauranodon nutans, and Professor Marsh regards it as the type of a new order 

 of Reptiles {^auranodonta). 



