CROCODILIA. 223 



vertebno are slightly amphicoelous. The limbs are typically crocodilian 

 in every respect, and the fore limb is not much smaller than the liinl 

 limb. The typical species is Notosuchus terrestris, with the skull about 

 O'ISm. in length. A closely related genus, Cynodontoaiichus, from the 

 same formation and locality, also exhibits the highly specialized dentition, 

 but has large canines in the lower jaw, crossing and working upon those 

 of the upper jaw. 



Sub-Order 3. Eusuchia. 



Like the Mesosuchia, the Eusuchia comprise both long- 

 snouted and broad-snouted crocodiles, besides intermediate 

 forms (Tomistoma). The majority, however, are of the broad- 

 snouted type represented by the Crocodiles and Alligators of 

 the present day. They all agree (i.) in the flooring of the 

 secondary nasal passage by plates from the pterygoid bones, 

 (ii.) in the enclosure of the eustachian canals by bone, and 

 (iii.) in the procoelous character of the vertebral centra. They 

 form so homogeneous a group that it is difficult to believe that 

 they arose from more than one common Mesosuchian ancestor ; 

 but Paleontology as yet does not afford any evidence on the 

 subject. It remains uncertain whether Teleosaurs passed into 

 Gavials, while Goniopholis-like Mesosuchians became Crocodiles 

 and Alligators, or whether the modern Eusuchia, as such, have 

 diverged from one central primitive type. The earliest known 

 proccelian vertebrae which seem to be crocodilian occur in the 

 English Purbeck and Wealden strata (Heterosuchus), but they 

 are too unsatisfactory for discussion ; the same remark applies 

 to other detached vertebrae found in the Cambridge Greensand. 

 Thoracosaurus, from the Cretaceous of New Jersey, U.S.A., 

 Holland, and France, is a Gavial-like Eusuchian with a remnant 

 of the antorbital vacuity found in some Teleosaurs ; but this 

 persistent character may not be of much significance. 



The only interest of the extinct Eusuchian Crocodilia con- 

 sists in their geographical distribution, and in the intermediate 

 (generalized) character of those dating back to the Lower 

 Tertiary. Skulls indistinguishable from that of Tomistoma (now 

 living in the Malay Archipelago) occur in the Miocene of 

 Austria and Malta. Remains of more typical Gavials are met 

 with in the Pliocene of the Siwalik Hills, India, and in the 



