OKOCODILIANS, LIZARDS. AND SNAKES. 161 



LORICATA. 



Loricata Mehre.m, Tentamou Systematis Amphibioruin, 1820, p. 7. 

 Emydosauri Gray, Aimals of Philosophy (2), X, 1825, p. 195. 

 Crocodili Wagleh, Syst. Amphib., 1830, p. 139. 

 Crocodilia Owen, Kept. Brit. Assoc. Adv. Sci., XI, 1841, p. 65. 



Quadrate bone united by immovable suture with tbe adjacent ele- 

 ments; 2 postorbital longitudinal bars; cervical and dorsal ribs mostly 

 two-headed, the capitulum articulating with the centrum, with or with- 

 out parapophyses, and the tuberculum with the diapophyses. Sacrum 

 composed of but few vertebrie. Acetabulum closed. Sternum and 

 interclavicle j)resent; abdominal ribs not connected with the true ribs, 

 and composed of separate segments. Bones of proximal series of car- 

 pus and tarsus specialized. Teeth in alveoli. 



Ventricle of the heart divided. Two aorta roots. Epencephalon with 

 vermis and flocculi. Copulatory organ single. Anal orifice longitudi- 

 nal. 



The order of the Loricata appeared in Triassic time, and has con- 

 tinued up to the present day. The Triassic types differ from those of 

 subsequent ages, so that they represeut a suborder distinct from the 

 latter. In Jurassic and Cretaceous time the order was represented by 

 the greatest number of genera and species. Their distribution has 

 been cosmopolitan since their appearance. The affinities of the order 

 are with the Dinosauria, with which they are connected by the sub- 

 order Sauropoda of the latter. 



The suborders differ as follows: 



External nares posterior; internal naros less posterior; pterygoids articulating 

 with quadrate; postfrontal and postorbital bones distinct Parasuciiia. 



Internal nares more posterior; external nares anterior; pterygoids not reaching 

 quadrates; postfrontal and postorbital bones not distinct Eusuchia. 



The Parasuchia include, so far as yet known, the single family of the 

 Belodontidie. They are restricted to the Triassic system. The fam- 

 ilies of the Eusuchia are the following: 



I. Vertebrin amphiplatyan. 



Posterior nares more anterior; sphenoid axis horizontal; postorbital border 



on plane of adjacent bones Teleosaukid.e. 



Postorbital border internal to plane of adjacent bones Goniopholidid.e. 



II. Vertebne procadoiis. 



Sphenoid vertical ; postorbital border internal to adjacefnt plane. Crocodilid/E. 



The first two families do not extend beyond Mesozoic time. The 

 Crocodilida'. commence in North America in the Upper Cretaceous; in 

 other i)arts of the world in the Eocene. We have to do with this fam- 

 ily only in the present work. Its genera differ as follows : 



I. A preorbital foramen. 



Dorsal vertebrae with rudimontal hypapophyses; muzzle elongate, nasal bones 



not reaching nares Thoracosaiirus Leidy. 



NAT MUS 98—11 



