MAMMALIA. 315 



e. Anterior limbs not adapted for flight ; ulna and radius not united ; 

 hand normal ; mammae usually abdominal. 



LNSECTIVORA, XLIX. 



ee. Anterior limbs adapted for flight; ulna and radius united; bones 

 of hand and fingers much elongated, supporting a thin, leathery 

 skin, extending along sides of body to the posterior limb^ ; 



mammae pectoral CHIROPTERA, L. 



cc. Brain with a relatively large cerebrum overlapping much, or all, of 



the cerebellum and optic lobes. (EducaMlia .) 



f. Posterior limbs absent, the pelvis rudimentary; anterior limbs 



reduced to broad flattened paddles, without distinct ringers or 



claws; no clavicles; tail with a broad, horizontally placed 



caudal fin; cervical vertebrae more or less grown together; 



carnivorous CETE, LI. 



ff. Posterior limbs and pelvis well developed; anterior limbs with 



hoofs, claws, or nails. 



g. Femur and humerus not exserted beyond the common integu- 

 ments of the bod\'; clavicles more or less rudimentary; 

 mammae abdominal or inguinal. 



h. Feet with hoofs ; molars mostly with grinding surfaces ; in- 

 cisors various; no tusks; developed toes, 1 to 4; herbivor- 

 ous UNGULATA, LII. 



M. Feet with developed claws; canines specialized; molars, 

 one or more, sectorial, adapted for cutting; incisors |; 



carnivorous FER^E, LIII. 



gg. Femur and humerus exserted; feet with distinct toes which 

 are provided with nails ; clavicles present ; an inner digit 

 of hand (thumb) opposable to the others ; orbits encircled 

 by bone and directed forwards ; mammae pectoral, two in 

 number (rarely also an inguinal pair). PRIMATES, LIV. 



ORDER XL VII. MARSUPIAL! A. (THE MARSUPIALS.) 



Young developed without a placenta, and born at a very early 

 stage and incomplete condition of development. The young at 

 birth are usually placed in an abdominal pouch formed by a fold of 

 skin about the milk glands of the mother, where they remain for a 

 considerable time. Reproductive organs in both sexes of peculiar 

 structure, nearly all the parts being double in the female. Skele- 

 ton showing numerous peculiarities, the teeth usually more numer- 

 ous than in the higher Mammals. Brain small, the corpus callosum 

 rudimentary. Heart with two venae cavae. This large group is 

 chiefly confined to Australia. It represents an early or primitive 

 type of Mammalia, which has now become extinct in most parts of 

 the world. The single non-Australian family approaches most 

 nearly to ordinary Mammals. (Lat., marsupium, pouch.) 



Families of Marsupialia. 



a. Tail long, prehensile, nearly naked ; feet plantigrade. 5-toed, the first toe 

 thumb-like and without claw ; teeth 50. ... DIDELPHIDID.E, 180. 



