AND AYES OF NORTH AMERICA. 



1 75 



Arohaeopteryx. Rhamphorhynchus, which most, resembles it, differs in its simple teeth; and Dimorphodon in its 

 opistho- or amphicoelian vertebrae. 



Dimorphodon Owen has been up to the present time the oldest type of the Pterosauria, I), macronys Buck, occur- 

 ring in the Lower Lias of England. The present species will therefore be of much Interest, as originating in a, sup- 

 posed Triassio formation, but indicating with the Megadactyhis more probably Jurassic age. Perhaps the strata con- 

 tinuous between its horizon and that of Belodon* (Be. carolinensis) will point to the correctness of Wheatley'st pro- 

 position, that "The true position may be determined like the Ban Casciano beds, intermediate between the, Liassic 

 and Triassic formations, and forming a, separate group, containing like (hose beds its own peculiar fossils." 



As the first Pterosaur found in the Mesozoic formations of North America, the species is of interest as indicating 

 the future discovery <>f other ['onus of the same sub-class, which wide distribution will furnish additional illustra- 

 tions or the persistency of evanescence of types. Some of the remains, however, probably belong to the Bymphypoda. 



Fig. 46. 



r 



I» Y T II O N O JH <t> IS V II A. 



Cope Proceed., Boston Soc. Nat. Hist., 1869, p. 258. 



The genus LYEosasaurus, since the discovery of the large specimen in the St. Peter's 

 Mount, at Maestricht, has been a subject oi discussion by many palaeontologists, and ever 



H'ia. Cope, Proc lings Academy, 1886, 



f In SlUlman's Journal ofScience and Arts, xxxlj, 1861. 



