Vol. XXIII, pp. 57-60 April 19, 1910 



PROCEEDINGS 



OF THF, 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE GENERIC NAME OF THE H0U8E-RATS.I^ *■ 

 BY GERRIT S. MILLER, JR. 



The generic name Mus, is currently applied to lioth house-mice 

 and house-rats, as well as to an assemblage of rat-like species 

 comprising perhaps the greater part of the sub-family Murinae. 

 This arrangement involves many inconsistencies, the most glar- 

 ing of which is probably the close association of the house-mice 

 with the rats. The two groui)s are in fact generically distinct, 

 the rats retaining a primitive type of dentition, in which the 

 anterior molar shows no tendency to assume the chief function 

 of the toothrow, and the posterior molar remains a large, func- 

 tionally important tooth, while the house-mice and their allies 

 have a highly specialized toothrow in which the first molar is of 

 much more mechanical importance than the other teeth com- 

 bined, and the third tooth is greatly reduced. The incisors in 

 the house-mouse group are also noticeably specialized . With the 

 house-mice and their European and Central-Asiatic allies must 

 be associated the Indian and African group commonly known as 

 Leggcula, the main peculiarities of which are precisely the same. 

 In its most extreme deye\o\')ment Leggadn differs fi-om the house- 

 mice in the more pronounced reduction of the hinder molar and 

 in the further enlargement of »?' by the addition of a supple- 

 mental anterioi" transverse enamel ridge; but on taking into 

 consideration the numerous recently described species it seems 

 impracticable to retain tiie two groups as distinct genera. 



The type of the Linna^an genus M^s is by tautonymy muscidus, 

 since this is the only inclujiled species " possessing the generic 

 name as * * * [a] synonym."* This name must therefore be 

 restricted to the house-mouse-Le^p'ac/a group. 



* International Code, article 30. 



12— Proc. Biol. Soc. Wash.. Vol. XXIII, 1910. (57) 



