2 Memoirs of the Indian Museum. [Voi,. I, 



However, along with this came a suggestion that the subject was in such a state 

 that any contribution would be of value, particularly when such unlimited material 

 was at hand. Accompanying the suggestion came instructions how to carry it out, 

 the requisite measurements to be taken and points to be noted. I must here express 

 my deep indebtedness to. Colonel Alcock, I. M.S., and to Dr. Annandale for the encour- 

 agement and the assistance they have given me, putting all the facilities of the 

 Museum at my disposal. My thanks are also due to Mr. I. H. Burkill and his 

 brother and to Colonel Bingham for the great trouble they have taken over the 

 reproduction of the plates illustrating this paper. 



I have now recorded the measurements of over 200 rats, and must have roughly 

 examined the external characteristics of some 2,000. When I began to work I was 

 entirely ignorant of the subject, and could only group my observations vaguely, accord- 

 ing to such external characteristics as size, colour, the proportionate length of the foot 

 or the tail, the colour of the tail, and the like. It was gratifying to find later that 

 a detailed examination of the skulls and dentition confirmed the validity of the group- 

 ing ; without knowing what rats I was dealing with , I had separated them correctly. 



HISTORICAL. 



A brief note on the history of the study of the Indian Murinse may be of some use, 

 at least to the beginner, as an indication of the existence of three main epochs in 

 the history of the subject. The first epoch is that in which species were named 

 in the most loose and unsystematic manner, vitiated by imperfect description and 

 examination of a very limited number of specimens, with the result that complete 

 confusion ensued. This epoch may be said to have closed in 1863, when Blyth wrote 

 his Memoir on the Rats and Mice of India. ^ In this a complete collection was made 

 of all references to all Indian species, but practically nothing was done to systematise 

 the some fifty species regarding which references were collected. Dr. Jerdon accepted 

 Blyth's work, adding little to it, and except for Dr. Anderson's able and exhaustive 

 paper on the subject of the subgenus Nesokia,^ nothing was done till Thomas in 

 1 88 1 wrote his epoch-making memoir on the Indian species of Mus. This work was 

 based on an examination in England of 450 Indian specimens, of which no less than 

 180 had been preserved in spirit. 



The main feature of Thomas's invaluable work was the reduction of a crude col- 

 lection of 90 names into a co-ordinated system containing only 19 valid species, so that 

 from the synopsis it was easy to dentify a specimen. Outstanding facts in the 

 paper are the demonstration from a series of skulls of M. alexandrinus var. nitidus 

 that the proportionate length of the nasals is a character so liable to individual variation 

 as to be useless as a specific character, and that the same is the case with the 

 presence or absence of spines in the fur. At one time this latter character was made 



' Journ. Asiat. Soc. Bengal, vol. xxxii, p. 327. 

 '^ Journ. Asiat. Soc, Bengal, 1878, vol. xlvii, part ii, p. 214. ^ Proc. Zool. Soc, 1882, p. 257. 



