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NORTH AMERICAN FAUNA. 



[No. 10. 



appearance, it is completely surrounded by the small B. carolinensi''. 

 It is in etfect therefore an insular form, like those inhabiting the sum- 

 mits of high mountains within the range of more southern species. Its 

 semi-aquatic habits, necessitated by its watery environment, have led 

 to the unusual development of the hind feet, and the distinctive char- 

 acter of the molars may have resulted from some peculiarity of food. 



Aleasiirements (taken in flesh). — Tjqie specimen: Total length, 118 

 mm.j tail vertebrae, 28 mm.; hind foot, IG mm. Average of 13 speci- 

 mens from type locality : total length, 119.5; tail vertebrae, 26.45 ^^^^^ 

 foot, 16. 



Subgenus CRYPTOTIS Pomel. 



1848. Cryptotis Pomel, Archiv. Sci. Pliys. and Nat. Geneve, IX, Nov. 1848, 249. 



Type, Sorex cinereus Bach. ( — Sor ex parvus Say). 

 1877. Soriciscus Coues, Bull. U. S. Geol. and Geog. Surv., 1877, 649. "Type Sorex 



parvus Say or S. cinereus Bach." 



Diagnosis. — Teeth, 30 j unicuspids, 4, never in two pairs; fourth always 

 smaller and usually minute; basal lobe of middle incisor a rounded 

 cusp (pi. 3, figs. 2, 3, 13, 14). Brain case more or less arched, highest 

 anterior to lambdoid suture ; j)lane of occiput arched. 



Geographic distrihution. — Broadly, the less arid parts of the Austral 

 region in Mexico, Guatemala, Gosta Kica, and the eastern United States. 

 One species (parva) pushes northward in the United States through the 

 Upper Austral or Carolinian zone; one [tropicaUs) reaches southward 

 into the Tropical region of Mexico and Guatemala, and several asceud 

 the mountains of Mexico into the Boreal. 



Kumler of representatives. — The great majority of American Short- 

 tailed Shrews belong to the subgenus Cryptotis. Sixteen species and 

 subspecies are here recognized, contrasted with 4 of Blarina proper 

 and 2 of Kotiosorex. The subgenus attains its greatest development 

 in the highlands of southern Mexico. The species may be roughly 

 assembled in 4 groups : (1 ) The parva group, comprising_2?arra, ^onfZa/i«, 

 herJanclieri, trojncalis, soricina., orophila^ and ohsciira (the latter 

 approaching the next); (2) the mexicana group, comprising mexicana, 

 goJdmani, peregrina, machetes, nigrescens, and nelsoni; (3) the altieola 

 group, comprising altieola and fossor; and (4) the magna group, com- 

 prising, so far as known, the single species of that name. 



It is of little consequence whether closely related forms are treated 

 as species or subspecies. When intergradation is known or strongly sus- 

 pected, or the degree of differentiation slight, the animals are classed 

 as subspecies. In the case of two the smaller forms here accorded 

 specific rank (floridana and herlandieri) it is not improbable that in 

 each instance intergradation will be found with parva (but not with 

 one another) when specimens are collected from intermediate localities. 



