ORDER SAUROPTERYGIA. 



IO71 



have a small notochordal canal, and are small in comparison to the 

 neural arches ; while the ribs seem to have been anchylosed to the 

 vertebrae, and were of great thickness, like those of the next family. 

 The system of abdominal ribs was strongly developed. The skull 

 is much elongated, and has slender recurved teeth, which were in 

 all probability implanted in distinct alveoli. The pectoral girdle 

 appears to be very similar to that of the Nothosauridce, the pre- 

 sumed interclavicle not being T-shaped ; and a similar close re- 

 semblance is presented by the pectoral limb (fig. 990), in which 

 the humerus has an entepicondylar, or ulnar, foramen, like that of 

 Mammals. The pelvis is considered to have had only a very 

 small obturator foramen ; the ischia and pubes forming broad 

 expanded plates like those of Amphibia and other Sauropterygia. 

 The terminal digits were devoid of claws ; and the feet were prob- 

 ably webbed like those of frogs. 



Dr Baur makes this genus the type of the order Proganosauria, 

 in which he would also include the undermentioned genus Palcso- 

 hatteria; and regards this order as the connecting-link between Am- 

 phibians and Reptiles. Although there is something to be said in 

 favour of this view, yet the manifest affinity of Mesosaurus to the 

 more typical Sauropterygia, and of Palceohatteria to the Rhyncho- 



Fig-_ 991. — Palatal aspect of the cranium of Nothosaurus mirabilis ; from the Muschelkalk. 

 One-eighth natural size, pmx, Premaxilla ; nar, Posterior nares ; vo, Vomer ; mx, Maxilla ; 

 pal, t Palatine; pt, Pterygoid; a, Ala of do. ; b, Quadratic ridge of same ; qu, Quadrate; oc, 

 Occipital condyle. The posterior extremity of pal is probably formed by a distinct transverse 

 bone. 



cephalia, seem to render it more advisable to refer those genera 

 to the two orders in question, of which they will respectively form 

 the most generalised stage. By this arrangement the intimate con- 

 nection of both orders with the Amphibia will be made manifest. 



Family Nothosaurid^e. — In this family, which comprises some 

 forms of large size, the limbs were furnished with claws, and adapted 

 to a certain extent for walking. In the skull the pterygoids either 



