78o MAMMALIA. 



number, are clawed, and the animals walk in plantigrade 

 or semi-plantigrade fashion. In most, the mammae are 

 thoracic or abdominal. 



The cranial cavity is small; the skull is never high; the 

 facial region is long ; the zygomatic arch is slender or 

 incomplete. Except in Potamogale^ there are clavicles. 



There are never fewer than two pairs of lower incisors. 

 The enamelled molars have tuberculated crowns and well- 

 developed roots. In many cases it is not easy to distinguish 

 the usual division of the teeth into incisors, canines, pre- 

 molars, and molars, but in many the dentition is typical 



3, i> 4, 3 = 44. 



In the hedgehog, according to Leche, i. 3, pm. 2, m. 1-3, 

 of the upper jaw, and i. 3, c., pm. 3, m. 1-3, of the lower 

 jaw, are persistent milk-teeth, but, according to others, the 

 milk-teeth are represented by mere rudiments ("prelacteal 

 germs "), and the functional teeth correspond to the perma- 

 nent set of other mammals. 



The* cerebral hemispheres are smooth, and leave the 

 cerebellum (and sometimes the corpora quadrigemina) 

 uncovered ; the olfactory lobes are large ; the corpus 

 callosum is short and thin. Thus, as regards the brain, 

 the Insectivora represent a low grade of organisation. 



The stomach is a simple sac ; the intestine is long and 

 simple, but the vegetarian forms have a caecum. In most 

 there are odoriferous glands, axillary in shrews, but usually 

 near the anus. 



The testes are inguinal or in the groin, or near the 

 kidneys, not in a scrotum. The penis may be pendent 

 from the wall of the abdomen, but is usually retractile. 

 There is a bicornuate uterus. Several and usually many 

 offspring are born at once. 



The allantoic placenta is discoidal and deciduate. There 

 is a provisional yolk-sac placenta. 



Insectivora are represented in the temperate and tropical 

 zones of both hemispheres, but not in S. America (except 

 in the Northern Andes) nor Australia. In the former 

 continent their place is taken by the insectivorous opossums. 



Examples. The hedgehogs (Erinaceus), throughout Europe, Africa, 

 and most of Asia, dentition \~ '> the shrews (Sorex], in 



