640 BULLETIN UNITED STATES GEOLOGICAL SURtEY. 



south of the United States, the subtropical extension of the family further 

 being represented, as far as is now known, only by one or two species of 

 Blarina, and by the still undescribed species of Sorex (?) named Corsira 

 temlyas by Gray. 



Blarina, the genus of Soricidw which contains the most species 

 among those peculiar to this continent, is on the whole rather southerly 

 in distribution. It is not known to occur much beyond the northern, 

 border of the United States, nor has it been detected on the Pacific 

 side. A species of Blarina proper {i. e,, of Blarma with 32 teeth) is the 

 commonest representative of the family in New England and adjacent 

 portions, and with another species (or variety) extends more sparingly 

 into a part at least of the Southern States. Westward, I have no speci- 

 men of this subgenus beyond the plateau-region whence Say described the 

 original " Sorex^^ hrevicaiida; but it probably reaches the Eocky Mount- 

 ains at least. Blarina of 30 teeth is still more decidedly southerly. I 

 am not aware that it is known north of the Middle States, and it appears 

 to be the most abundant and characteristic representative of Soricidce 

 in various South Atlantic States, as the Carolinas and Georgia. One 

 species (if not also a second) occurs throughout the Southern States, 

 and extends through the Western States to Kansas and Nebraska, if 

 not farther, and at least as far north as Council Bluffs. This same sub- 

 genus, to be characterized beyond as iSoriciscus, extends through Mexico 

 to Costa Rica, being represented south of the United States by at least 

 two species. With the exception of one Mexican species of Sorex (Notio- 

 sorex), and one Central American species, perhaps a true Sorex, it is the 

 only known subtropical representative of the Sorieidce. 



§ 5.— DETERMINATION OF THE AMERICAN GENERA AND 

 SUBGENERA OF SOBICID^. 



According to reliable authority, the Old World Shrews occur under 

 three principal moditications, represented by as many leading genera 

 and their respective intimate associates. These three are Sorex, Croci- 

 dura, and Crofisopus. 



Sorex, the most generalized type, is the only one which is known to 

 occur in America. With its Old World subdivisions I am not familiar. 

 Paradoxodon and Soriculus appear to be the most prominent. The 

 American species of Sorex are nearly all strictly congeneric with Sorex 

 vulgaris,* having 32 colored teeth. I am uncertain to which one, if to 

 any one, of the subdivisions the type Microsorex of 30 colored teeth may 

 belong. We have nothing in America exactly like Croeidura (type G. 

 aranea) of 28 uncolored teeth ; but the new subgenus Notiosorex, of 28 

 nearly colorless teeth, large naked ears, etc., seems to answer for this 

 type. Crossopus, embracing the Old World Water-shrews of 30 colored 



* Which I here consider the type of Sorex, though some authors restrict the uaine to 

 a species with white teeth (Hydrosorex Duv., 1834). 



