484 ZOOT.OGY sect. 



the manns and the first and fifth of the pes are never longer than 

 the others. One tooth on each side in each jaw — the last pre- 

 molnr in the upper jaw and the first molar in the lower, is always 

 modified to form the carnassial or sectorial tooth with a cutting 

 edge which bites against the edge of the opposed tooth. 



This sub-order comprises the Cats (Felidcc), Civets ( Viverridw), 

 Hyffinas {Hywnidcc), Dogs {Ccnidcc), Bears (Ursidce), Weasels 

 (Mu.stelidcv), and Otters (Lutridce). 



Sid)-order !>. — Pinnipedia. 



Carnivora in which the limbs are adapted to an aquatic life, the 

 proximal segments being short, the distal elongated and webbed 

 between the digits ; with five well-developed digits in each manus 

 and pes, the first and fifth of the pes being larger than the others. 

 The number of incisors is reduced, and there are no carnassials. 

 The cerebral hemispheres are very richly convoluted. 



This order includes the Eared Seals {Otariidai), the Earless 

 Seals (Fhocidcc), and the Walruses (Trirhcchidce). 



Order C. — Rodentia. 



Vegetable-feeding Eatheria, mostly of small size, with furry 

 (sometimes spiny) integument, clawed digits, and usually planti- 

 grade limbs. A clavicle is usually present. The dentition is 

 diphyodont ; there are no canines, and there are never more than 

 two incisors in the lower jaw and usually only two in the upper — 

 all elongated, chisel-like, and growing from persistent pulps ; the 

 premolars and molars are usually few, and in many cases also 

 grow from persistent pulps. There is a large ca-cum. The 

 cerebral hemispheres have in most instances smooth surfaces, and 

 do not much overlap the other parts of the brain. The testes 

 are retained in the abdomen or descend to the groin. The utei'us 

 is two-horned or double. The placenta is deciduate and disc- 

 shaped (discoidal). 



This extensive order includes the Eats and Mice {Murid(v), 

 Hares and Eabbits {Leporldcc), Squirrels {Sciurid(c), Jerboas 

 {Dipodidce), Beavers {Cnstorida^, and Porcupines {Hjjstricidce). 



Order 7. — Insectivora. 



Small insectivorous Eutheria with the nose usually produced 

 into a short, soft muzzle, with furry (sometimes spiny) integument, 

 clawed digits, and usually pentadactylc plantigrade limbs. The 

 dentition is diphyodont and complete, and all the teeth are rooted ; 

 the incisors are small ; there are never fewer than two incisors on 

 each side of the lower jaw ; the molars are small and provided 

 with pointed cusps. A clavicle is present. The brain is simple 



