10 



Records of the Indian Museum. 



[Vol. Ill, 



Measurements of forty-five skulls of Mus rattus from Calcutta. 



Measurements of skulls of " types " or co-types of various species 

 of Indian Rats {W. L. Sclater). 



These figures show that the " types" of six distinct species 

 together show a smaller range of variation than forty-five chance- 

 taken rats from one town. Sclater's records are, as a whole, higher 

 than Hossack's. This must be because in ^measuring the total 

 length of the skulls the former did not include the incisor teeth ; 

 consequently the percentage values of the other features were 

 slightly raised. 



In the skulls from Calcutta the palatine foramen is sometimes 

 greater, sometimes less, than the molar series. Mus mettada, Mus 

 decumanus, and perhaps Mus jerdoni have their own skull types and 

 so are excluded. 



Species of rats from other parts of the Oriental region do not 

 usually show wider variation in the proportion of their skulls than 

 those presented by Hossack's measurements. 



The measurements of three species from the Malay region 

 will be given ; th^y have not been specially selected but are of the 

 three new species of Mus recently discovered in that region. 



