No. 1.] ARRANGEMENT OF THE SAUROPSWA. 97 



but that the Ichthyopterygia must have taken their origin from 

 such a one I have no doubt.^ 



The Sauropterygia and Testiidinata. 



This group of Reptiles is classified by Cope with the Synapto- 

 sauria, which have but one rib articulation. This is not correct; 

 the oldest Sauropterygia, the Lariosauridae and Nothosauridae, 

 and even Plesiosaurus, have two-headed ribs in the cervicals and 

 the former families even in the anterior dorsals. The posterior 

 dorsals have the capitulum and tuberculum united, and therefore 

 are morphologically two-headed. 



It always seemed difficult to determine the systematic position 

 of the Sauropterygia. Huxley considered this group allied to 

 the Crocodilia, especially to the Teleosauridae ; Owen compared 

 it with the Testudinata. 



That they descended from land-living reptiles is certain.^ 



The Sauropterygia begin in the Triassic with the Lario- 

 sauridae and Nothosauridae. They are in no direct relation 

 to the Ichthyopterygia. The skull and shoulder-girdle are 

 entirely different in both. 



The skull is very characteristic. It resembles the Rhyncho- 

 cephalia and old Crocodilia (Belodon, Teleosaurus) ; the 

 parietal foramen is present. The postorbital is free or united 

 with the postfrontal. The whole shape (at least of some forms) 

 resembles very much the skull of the Crocodilia; but one 

 character shows at once the specialization of the Sauroptery- 

 gian skull ; it is the absence of the lower temporal arch, as in 

 the Lacertilia ; a quadratojugal seems never to be developed. 



Another resemblance to the Rhynchocephalia consists in the 

 structure of the abdominal ribs. 



If we compare these elements in the Lariosauridae and 

 Nothosauridae with those in Sphenodon we find exactly the 

 same condition. In Lariosaurus and Sphenodon they are 

 entirely identical, as the figures of Deecke prove.^ 



'The Baptanodontia (Sauranodontia), Marsh, are specialized forms of the Ichthy- 

 opterygia, like the Mystacoceti among the Cetacea, and the Pteranodontidse among 

 the Omithosauria. 



*Baur, G. Bemerkungen iiber Sauropterygia und Ichthyopterygia. Zool. Anz., 

 No. 221, 1886. 



^ Deecke, W. Uber Lariosaurus und einige andere Saurier der lombardischen Trias. 

 Zeitschr. Deutsch. Geol. Ges. Bd. 38. PI. in. Fig. i. 



