EMTDOSAURIA. 273 



Order EMYDOSAURIA. 



Emydo-Saiiriens, Blainville, BuU. Soc. riiilom. 1816. 

 Loricato, Merrvin, Tent. Si/st. Aniph. 1820. 

 Emydosauri, Gray, Ann. Phil. (2) x. 1825. 

 Crocodili, Wagler, Syst. Amph. 1830. 



Quadrate bone immovably united to cranial arches ; two hori- 

 zontal bony temporal arches. Cervical and dorsal ribs mostly two- 

 headed, the middle dorsals articulating with tho transverse processes 

 of the neural arch. Sternum and interclavicle present ; seven or 

 eight transverse series of " abdominal ribs," not connected with the 

 vertebral ribs, each composed of four ossicles forming an angle 

 directed forwards. Teeth present in the jaws, implanted in alveoli. 

 Ventricle of the heart divided by a complete septum. Pectoral and 

 abdominal cavities separated from each other by a muscular dia- 

 phragm. Anal opening longitudinal. Copulatory organ present, 

 simple. 



The existing members of this Order, the most highly organized 

 of all recent Keptilia, cannot in my opinion be divided into several 

 families. The fact that Tomistohia is altogether quite as much 

 related to the long-snouted Crocodiles as to the true Gavial is 

 opposed to the separation of the GaviaUdce. The only constant 

 important character between the Crocodiles and the Alligators is 

 the increased number of mandibular teeth in the latter, which is 

 the same as in Tomistoma. The weU-known Cuvierian character of 

 the fourth mandibular tooth fitting into a notch in CrocodUus and 

 into a pit in Alligator is not absolutely diagnostic, since, as already 

 observed by Huxley, specimens of the short-snouted Crocodilus 

 j^alustris occur which agree in this respect with the Alligators, 

 whilst, on the other hand, Cope has described a supposed Alligator in 

 which the fourth tooth, on one side, fits into a notch. The short- 

 snouted species of Crocodilus and Osteolcmius further agree with the 

 Alligators in the mandibular teeth biting inwards of the maxillary 

 teeth instead of between them. Osteokcmus, although agreeing 

 with Crocodilus in its dentition, stands in most other respects nearer 

 the Alligators. A rather trifling character, recently pointed out by 

 Baur, viz. the absence of a more or less developed pointed process 

 on the free border of the quadratojugal, distinguishes Allvjator and 

 Caiman from the other Crocodilians 



