4 THE EXTINCT BATRACHIA, REPTILIA 



Nervous System. Cerebral hemispheres larger than optic lobes, extending over and con- 

 cealing optic thalami, and with the lateral ventricles on their order side. 



Fornix and arbor vita? none ; medulla oblongata abruptly curved ; olfactory lobes terminal 

 pedunculate. 



Circulatory System. Heart with three or four chambers. 



Aorta ivitli two roots, and rarely an additional bow ; no bulbiis arteriosus. 



AVES. 



Osseous structure as in Reptilia, except metatarsal and usually metacarpal bones are con- 

 fluent Avith each other, and with the carpal and second series of tarsal bones ; first series 

 of tarsals confluent with tibia. 



Pubis turned backwards and more or less confluent with ischium. 



Nervous System. Cerebral hemispheres larger than optic lobes, and concealing optic 

 thalami with the lateral ventricle. 



Fornix and arbor vitce present ; medulla oblongata bent; olfactory lobes inferior sessile. 



Circulatory System. Heart with four chambers. 



Aorta with one root turning to the right, no bows, and no bidbus arteriosus. 



Class I.-B^lTR^CHI^. 



The vomer is double, and usually bears teeth in this class; the premaxillary is single 

 or double* Teeth never planted in deep alveoli. 

 There are six orders, as follows: 



TRACHYSTOMATA. 



Caudal vertebra; and frontal bones distinct. Inferior pelvic elements not confluent. 

 O. o. maxillaria, prefrontalia, palatina and pterygoidea wanting; nasalia present. 

 Ethmoid, two lateral pieces, each forming part of palate. 



Mandible toothless, condyloid, teeth pleurodont. No "postorbital and supertemporal 

 bones." First pair ceratohyals distinct. 



* Two premaxillary bones are usually ascribed to the Batrachia, but in many Salamanders they are confluent. 

 Thus while they are double in Salamandra, they are single in Hemisalamandra, Triton and Diemyctylus. In 

 Amblystomidaj they are double. Among Plethodontidai, they vary. Of Plethodontine genera Batrachoseps and 

 Stereochila (Cope gen. nov. for Pseudotriion marginatum Hallow) have them single, and Plethodon double. Of 

 Spelerpine forms, Manculus (Cope gen. nov. for Salamandra quadridigitata Holbr.) Oedipus and Spelerpes have but 

 one, and Geotriton and Gyrinophilus (Cope gen. nov. for Salamandra salmonea Storer Pseudotriton salmoneus Bd.) 

 have two premaxillaries. Desmognathus and Amphiuma have single premaxillaries. 



