COUES ON INSECTIVOROUS MAMMALS. 645 



than the minute fifth, which occurs under the same conditions as last 

 described ; among the larger unicnspids there is either regular grada- 

 tion in size, or oftener the two first are coequal and larger than the 

 third and fourth, or again the third is decidedly smaller than the 

 fourth or second. In the species with 30 or 32 teeth, these conditions 

 are contrasted with those occurring in Blarina of the same numbers 

 of teeth; for in the latter the last two or three unicuspids are always 

 smaller than the first two, and much crowded. The large upper in- 

 cisor has a notched lobe or snag on its inner face, besides the strongly 

 developed posterior hook, which looks like a separate tooth, and 

 closely resembles the succeeding tooth. The under incisor has one, two, 

 or three denticulations on its cutting-edge, and reaches so far back 

 that the next tooth is entirely above it, while more or less of the suc- 

 ceeding tooth is likewise similarly placed with reference to the incisor. 

 The teeth are always colored (as they are also in Neosorex and Bla - 

 n«a), but in one subgenus the coloration is very slight. 



Such sum of characters is offered under three modifications (of the 

 teeth more particularly), which must be made the basis of subgeneric dis- 

 tinction, if not to be more highly appreciated. These are as follovrs : — 



a. Subgenus Sorex, L. (emend). 



Chaks. subg. — Teeth 32 {^). Upper unicuspids 5 ; the fifth minute, 

 but generally visible from the outside, though crowded between the 

 preceding unicuspid and the first molariform tooth, which are not in 

 contact; the first and second appreciably larger than the third and 

 fourth, which latter vary in size relatively to each other. Interior snag 

 and posterior hook of upper incisor well developed; lower incisor with 

 (normally) three denticulations ; whole of next tooth and half of the next 

 placed above incisor. Teeth all well colored. Coronoid of jaw long and 

 comparatively slender, nearly vertical. Skull moderately high behind, 

 the profile of the cerebral portion rising out of line with that of the 

 rostrum ; depth of rostrum (including closed jaw) less than that of cer- 

 ebral portion of the skull. Molar dentition moderate in development; 

 distance across outer edges of molars not over half the width of the 

 cranium ; length of series of molariform teeth not more than half the 

 length of the whole line of teeth. Tail not less than half the length of 

 the head and body, usually longer than the trunk alone. Central line 

 of heel naked. Ears moderately large. 



Type. — Sorex vulgaris, with which most of the American Sorices are 

 strictly con-subgeneric. 

 Group A. — Species with the third and fourth unicuspids approximately 



equal in size (both smaller than the first and second). 

 Group B. — Species with the third unicuspid decidedly smaller than the 



fourth (which is itself less than the second and first). (Confined to 



the Pacific Province.) 



[Subgg. Z> and c not American.] 



