328 CLASSIFICATION OF VERTEBRATES. 



feet pentadactyl, fifth toe reduced. ^Etosaurus, the best-known genus, 

 comes from the triassic of Wiirtemberg. Typothorax, triassic, New 

 Mexico. 



SUB-ORDER 2. PARASUCHIA. 



Extinct crocodilia with amphiccelous or flat vertebrae ; premaxilla very 

 long ; external nostrils separate and near orbits ; inner choana at anterior 

 end of palatines. Palatines and pterygoids not meeting in the middle line. 

 Supratemporal fossa small, infratemporal large ; parietals and frontals 

 paired; post orbitals present; coracoid short, discoidal ; clavicle present; 

 toes unknown. The species come from the trias of Europe, America, and 

 the East Indies. Belodon is found in Wiirtemberg, Pennsylvania, North 

 Carolina, and New Mexico. 



SUB-ORDER 3. EUSUCHIA. 



Crocodilia with amphi- or procoelous vertebrae ; premaxilla short ; ex- 

 ternal nares united and at front of snout; palatines and usually pterygoids 

 touching in the middle line, the choanae thus being carried far back. Par- 

 ietals and usually the frontals unpaired. Coracoid elongate ; no clavicle. 

 Pubis taking no part in the formation of the acetabulum. 1 Anterior feet 

 pentadactyl, posterior four-toed, the fifth toe being represented only by a 

 metatarsal. First three digits clawed. 



SECTION I. LONGIROSTRES. Snout very long, nasals never enter- 

 ing wall of anterior nares ; homodont dentition. The GAVIALID^E, of the 

 rivers of the Orient, is the only existing family. Rhamphostoma (Gavialis} 

 gangeticus comes from India. Rhynchosuchus is Australian. The earlier 

 longirostres have amphicoelous, the later procoelous, vertebrae ; the group 

 first appears in the lias. Telosaunts and Thoracosaurus are fossil. 



SECTION II. BREVIROSTRES. Snout shorter, rounded in front; 

 nasals forming part of wall of anterior nares or close to them ; heterodont 

 dentition. The ATOPOSAURID^E were small lizard-like marine forms from 

 the upper Jurassic. Goniopliolis (Diplosaums), of the family GONIOPHO- 

 LID^E, comes from the upper Jurassic of Belgium and Colorado. The 

 ALLIGATORID^E have existed since the cretaceous. Alligator contains 

 our North American species, A. Indus, as well as other species from South 

 America. These have the edge of the upper jaw without excavation for 

 fourth tooth of the lower jaw. In the CROCODILID^K such an excavation 

 occurs. The crocodiles occur in the tropics of both hemispheres, Crocodilus 

 americanus occuring in our southern states. 



1 This is the statement usually made ; but there is some evidence to show that the bone 

 usually called pubis is in reality the prepubis, the true pubis fusing after a time with the 

 ischium. 



