210 



PALEONTOLOGY 



pophyses with simple 

 heads ; those of the trunk 

 long and bent. 



Genus Nothosaurus, Mini- 

 ster. 



Sp. Nothosaurus mirabilis, 

 Minister. — In fig. 69 is given 

 an analysis of the chief charac- 

 ters as yet ascertained of the 

 species which may be regarded 

 as the type of its family ; by 

 comparing this diagram with 

 that of the Archegosaurus (fig. 

 65), the advance in the orga- 

 nization of the aquatic reptiles 

 will be readily traced and 

 understood. 



The skull is no longer de- 

 fended by a continuous covering 

 of sculptured plate-bones ; the 

 vacuities behind the orbits for 

 the temporal muscles are large 

 and widely open. These vacui- 

 ties are fenced externally by 

 two long and slender horizontal 

 bony bars ; the upper one is 

 formed by the mastoid (fig. 69, 

 8 ), and the post-frontal (12) ; 

 the lower one by the malar (27), 

 and squamosal (28) ; the latter 

 answering to the true zygomai ic 

 arch in Mammals. The squa- 

 mosal abuts by its hinder, ex- 



