OKDERS OF MAMMALIA. 



* YouDg'not born until of considerable size, and nearly perfect development, deriving 

 its nourishment before birth from the blood of the mother through the intervention 

 of a placenta ; vagina a single tube, sometimes with a partial septnm ; cerebral hemi- 

 spheres connected by a well-developed corpus callosum and a reduced anterior com- 

 missure. (Subclass Monodelphia.) 



t Brain with a relatively large cerebrum, behind overlapping much or all of the cere- 

 bellum, and in front much or all of thcolfactory lobes ; corpus callosum continued 

 horizontally backwards to or beyond the vertical of the hippooampal sulcus, develop- 

 ing in front a well defined recurved rostrum. (Super-order JSducabilia.) 

 Anterior and posterior limbs and pelvis well developed; legs with the proximal joints 

 (humerus and femur) not exserted beyond the common integument of the body. 



a. Digits with corneous appendages developed as claws ; teeth of three kinds; 

 canines specialized and robust ; molars, one or more in each jaw, sectorial, 

 adapted for cutting ; incisors i ; scaphoid and lunar bones consolidated, 

 placenta deciduate and zonary Cajrnivoea. 



flo. Digits with corneous appendages developed as hoofs; teeth of three kinds; 

 incisors various, often reduced or wholly suppressed, especially in upper 

 jaw; no developed tusks; scaphoid and lunar bones separate; placenta 

 non-deciduate (diffuse or cotyledonary. ) .... Ukgulata. 



tt Brain with a relatively sipall cerebrum, leaving behind much of the cerebellum ex- 

 posed, and in front much of the olfactory lobes ; corpus callosum extending more or 

 less obliquely upwards, terminating before the vertical of the hippocampal sulcus; 

 no well defined rostrum in front. (Super-order Inedueabilia.) 



I. Incisors (very variable in number without persistent pulps) never |ori; 

 canines present; molars with sharp and pointed tusks; lower jaw with 

 condyles transverse, received into special glenoid sockets. 

 V. Anterior limbs adapted for flight; ulna and radius] united [; bones of hand 

 and finger much elongated, supporting a thin, leathery skin extending 

 along sides of body to the posterior limbs; mammie pectoral. 



Cheiroptera. 

 CO. Anterior and posterior limbs adapted for walking or grasping; ulna and ra- 

 dius entirely or partially separated ; bones of hand and fingers normally 

 developed ; mammse abdominal. .... Insectivoka. 



bh. Incisors ^ rarely 1 ■ continually produced from persistent pulps, and growing 



in a circular direction; canines none; molars with ridged surfaces; lower 



jaw with condyles longitudinal, not in glenoid cavities, but gliding freely 



backwards and forwards in longitudinal furrows. . . Kodentia. 



** Young born of very email size, and imperfectly developed, never connected by a 



placenta to the mother ; when born, attached by her to the nipple, from which the 



milk is forced by the mother into the mouth of the young; cerebral hemispheres 



chiefly cobnected by a well-developed anterior commissure, the corpus callosum 



being rudimentary ; vagina more or less completely dividing into two separate 



passages. (Sub-clasa Didelphia.) Mabsupialia. 



