CHAP. XIII.] THE CAT'S FLACE IN NATURE. 459 



(13) Its cerebral hcmisplieres are large, and united by a corpus 



callosum. 



(14) There are small corpora quadrlgemina instead of large optic 



lobes. 



(15) There are hypoglossal nerves which perforate the exoc- 



cipitals. 



(16) The olfactory nerves being present,'* traverse a cribriform 



plate. 



(17) The ear has a tympanic membrane and an Eustachian tube. 



(18) The posterior nares open far back within the mouth. | 



(19) There are no gills at any time of life. 



(20) Eespiration after birth, is pulmonary only. 



(21) The heart consists of two auricles and two ventricles. 



(22) All the blood of the body traverses the lungs. 



(23) There is but one aortic arch. 



(2-1) There is a large anterior vena cava and a large posterior 

 vena cava. 



(25) There is a larynx. 



(26) The hinder end of the alimentary canal does not terminate 



anteriorly to the urinary outlet. 



(27) There is a complete diaphragm aiding respiration. 



(28) There are no fin rays. 



(29) The red blood-corpuscles are not nucleated, and the blood is 



warm. 

 *(30) There are cervical vertebrae. 



(31) In development an amnion is formed. 



(32) Cardinal veins, at first important, afterwards become subor- 



dinate to the venee cava:. 



(33) Kidneys replace transitory Wolffian bodies. 



(34) There is an allantoic placenta. :|: 



(35) There is a fenestra ovalis. 



_ § 12. We come now to the class Batrachia, which contains, be- 

 sides the frogs, toads, and commoner efts, certain noteworthy eft-like 

 creatures, such as the gigantic salamander of Japan and China, the 

 Menopoma, Amphiuma, Mcnohmnchus and Siren of the United States, 

 the Axolotl of Mexico, and the Proteus of the dark subterranean 

 caverns of Carniola and Istria. Besides these animals, the class also 

 contains certain limbless creatures which look like something between 

 snakes and earthworms. They have long, slender bodies, marked by 

 many transverse wrinkles, and are called Opliiomoiplia. Creatures 

 which lived during the deposition of the carboniferous strata, and which 

 are known as Lahyrinthodonta, are also included amongst Batrachians. 

 The common frog {liana tenqjoraria) may be taken as a type of this 

 class. This animal has two pairs of well but unequally developed 



* In a few mammals they are absent. 



t That they open into the mouth at 

 all, would serve to distinguish the oat's 

 class from all fishes save such as the 

 Lejaidosireii. 



+ In certain sharks a placenta is 

 formed, but by the intervention of the 

 umbilical vesicle. It is not therefore an 

 allantoic placenta. 



