Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/7

Rh SYNOPSIS OF THE PRIMARY TYPES EMBRACED IN THIS ESSAY.

THE Classes Aves, Reptilia, and Batrachia are those over which the present review extends. The classes of veretebrata not included are: the Dipnoi, Pisces, Elasmobranchi, Dermopteri, and Leptocardii and the Mammalia. The Ayes, Reptlia, and Batrachia are characterized and distinguished from all the other classes as follows: the points wherein they differ from each other are italicized.

BATRACHIA.

Axial elemzent of the brain chamber a single membrane bone, the parasphenoid ; occipital condyles two, on the exoccipitals.

Mandible compound, supported by quadratum.

A distinct corticoid bone.

Limbs when present ambulatory, attached anteriorly to a scapular arch which is free from the cranium.

Nervous System. Cerebral hemispheres larger than optic lobes, not covering the optic thalami, and with the lateral ventricle on their inner side.

Fornix and arbor vitæ none; medulla oblongata straight; olfactory lobes terminal, sessile.

Circulatory System. Heart with two and three chambers. Three or more aorta bows ; aorta with two roots from a ductus communis and bulbus arteriosus.

REPTILIA.

Axis of brain case, the bast-occipital and sphenoid elements developed in the primordial cartilage, the first with exoccipitals bearing one condyle.

Mandible compound, supported by quadratum.

Coracoid bone distinct.

Limbs the anterior attached to a scapular arch which is free from cranium

Metatarsals and metacarpals distinct; carpals and second row of tarsals also distinct; usually the first row of tarsals also

Pubis not in contact with ischia distally.