Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/8

 4 THE EXTINCT BATRACHIA, REFTILIA Nervous System. Cerebral hemispheres larger than optic lobes, extending over and con-cealing optic thalami, and with the lateral ventricles on their outer side. Fornix and arbor vitEc none; methdla oblongata abruptly curved ; olfactory lobes terminal peduneulate. Circulatory System. Heart with three or four chambers. Aorta with two roots, and rarely an additional bow ; no bulbus arteriosus. AYES. Osseous structure as in Iteptilia, except metatarsal and usually metacarpal bones are con-fluent with 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. Nei vows System. Cerebral hemispheres larger than optic lobes, and concealing optic thalami with the lateral ventricle. Fornix and arbor trace 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 bulbus arteriosys. Class I. B_A_TRA_CIIIA. 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: TRACIIYSTOMATA. Caudal vertebrae and frontal bones distinct. Inferior pelvic elements not confluent. 0. o. maxillaria, prefrontalia, palatina and pterygoidea wanting; nasalia present. Ethmoid, two lateral pieces, each forming pat of palate. Mandible toothless, condyloid, teeth pleurddont. No "postorbital and supertemporal bones." First pair ceratohyals distinct. Two premaxillary bones•are usually ascribed to the Batraehia, but in many Salamanders they are confluent. Thus while they are double in Salamandra, they are single in Hemisalamandra, Triton and Diemyetylus. In Amblystomithe they are double. Among Plethodontidse, they vary. Of Plethodoutiue genera Batrachoseps and Stereoehila (Cope gen. nov. for Pseudotriton marginatus Hallow) have them single, and Plethodon double. Of Spelerpine forms, Manetilus (Cope gen. nov. for Salamandra guadridigitata Holbr.) Oedipus and Spelerpes have but one, and Geotriton and Grinophilus (Cope gen. nov. for Salamandra salmonea Storer Pseudotriton salmoneus Bd.) have two premaxillaries. Desmognathus and Amphituna have single premaxillaries.