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In 1842,* Dr. Gray, selecting Mus hardwickii as his type, described the genus Nesokia, characterizing it thus, "cutting teeth very large, flat in front and smooth; grinders 3.3; front upper large with three cross ridges; the middle oblong, and the hinder much narrowed behind, each with two cross ridges; the front lower grinder larger, narrowed in front with three cross ridges; hinder each with two ridges, the hindermost smallest, rather narrowed behind: tail short, thick, with whorls of scales and scattered bristles: toes 4-5, moderate, the three middle sub-equal, long, the outer moderate: claws small, compressed: front thumb tubercular, with a rudimentary claw: ears moderate, naked. "This genus," Dr. Gray states, “is easily known from the rats (Mus) by the large size of the cutting teeth and the shortness of the tail: it appears," he continues, "to be intermediate between the Rats and Rhizomys.”
In 1839,† Sir Walter Elliot described the afore-mentioned rat from Southern India under the name of Mus (Neotoma) providens, identifying it with the Mus indicus, Geoff. and the Arvicola indica, Gray, mentioning its Canarese name Kok or Koku, but his identification of it with M. indicus Geoff. was erroneous, as Mus providens is undoubtedly a Nesokia. Prof. A. Milne-Edwards, who has kindly examined for me the type specimen of M. indicus, Geoff. in the Paris Museum, informs me that it is very nearly allied to Mus decumanus, and that, although it is a little smaller, its teeth have the same conformation; and he further observes that Mus indicus is perfectly different from the animal figured by Peters under the name of Spalacomys indicus. Mus providens, however, has a skull like that of S. indicus, as I have satisfied myself by the examination of the skulls of two of Sir Walter Elliot's specimens.
Sir W. Elliot, in considering Mus providens as identical with Arvicola indica, Gray, lends the weight of his authority to the view that I have been led to adopt regarding Arvicola indica, because there can be no doubt that they both belong to one sub-generic type of Mus.
On referring to the list of Mammalia in the British Museum, published in 1848, three specimens of a rat are mentioned under the name of Mus kokt from Madras, and presented to the British Museum by Sir W. Elliot, and in the Introduction to his List of Mammalia§ 1843, Dr. Gray states that the Mus koke and some other species of rats (Mus rufescens, &c.) described in the Magazine|| of Natural History, 1837, were founded on specimens sent by Sir Walter Elliot, and that they were au
* Ann. and Mag. Nat. Hist., Vol. X, 1842, p. 264.
§ Op. cit., 1843, p. vii.
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thentic specimens of the species described by Elliot in the Madras Journal of Literature and Science.* There can therefore be no doubt of the identity of Mus kok with Mus providens, and that the types, as stated in the 'List of Mammalia,' on the authority of Elliot, were from cultivated plains in the Madras Presidency, and from Madras itself. The figure of Arvicola indica, fortunately bearing the date, 1st May 1829, renders it impossible that any of Elliot's specimens could have contributed the type of that species, and, moreover, in the Proceedings of the Zoological Society of 1835, it is stated that it was figured from General Hardwicke's drawings.
In the 'List of Mammalia,' there is no specimen under M. kok, of which Arvicola indica was regarded by Dr. Gray as a synonym, that could have formed the type of the latter, as all the specimens of M. kok that have been mentioned were, with one exception, received from Sir W. Elliot. The exception is described as (e) a small rat with a very long tail: India: from Dr. Smut's Collection.' A very long tail would seem to be sufficient evidence that this was neither M. kok nor Arvicola indica. On again turning to the 'List of Mammalia,' we find that the type of Nesokia hardwickii was presented by General Hardwicke, and in connection with this it is noteworthy that animals from the North-West Provinces of India corresponding to the description of that species are remarkably like the drawing of Arvicola indica. Moreover, Blyth states that there is no rat in Bengal, nor apparently in Madras, corresponding to that figure, and by extensive research, I can confirm this statement.
In the Catalogue of the Specimens and Drawings of Mammalia and Birds of Nepal and Tibet, presented by B. H. Hodgson to the British Museum (1846), the Kok, M. providens, is assigned to Nesokia, a course which Blyth himself followed in his Memoir on the Rats and Mice of India and in his Catalogue of Mammals.
In 1842, Sir Walter Elliot presented two stuffed specimens of Mus providens M. kok, Gray, to the Museum of the Asiatic Society of Bengal and these specimens still exist in the Indian Museum. They apparently belong to the variety found in the red soil, and which Elliot says is much redder than the common Koku of the black land, and they are quite distinct from M. (N.) hardwickii.
On a review of these circumstances, I am disposed to make the suggestion that the rat figured as Arvicola indica, and which Gray considered to be the Mus indicus of Geoffroy, is in reality the rat described by him, first under the name of Mus hardwickii, and afterwards as Nesokia hardwickii ; and in connection with this view of the question, it is important to bear in mind that the figure of Arvicola indica was received from
* 1. c.
General Hardwicke who afterwards, in presenting to the British Museum the type of Gray's Mus (Nesokia) hardwickii, presented a rat agreeing with the figure of Arvicola indica. The type of Mus indicus with which Gray believed his Arvicola indica to be specifically identical was from Pondicherry, and as has already been stated, it is a true rat allied to M. decumanus, and perfectly distinct from the animal figured under the name of A. indica, but, moreover, no rat has been obtained at Pondicherry at all corresponding specifically to the Mus (Nesokia) hardwickii with which the figure of Arvicola indica agrees.
The specimens of Mus providens in the Calcutta Museum are distinguished from Mus (Nesokia) hardwickii by their much narrower incisors, smaller molars, and by a long but narrow anterior palatine foramen, an opening which is very short in Mus (Nesokia) hardwickii, as is seen in Peters' characteristic figure of the so-called Spalacomys indicus, but the form of the skull is the same, both differing in the same respects from Mus. I have had the Madras rat alivet and have observed that it has the deep and rather short muzzle of Nesokia, with incisors broader than those of ordinary rats, and with the molars, when worn down, having the general characters of Nesokia. These rats, coming as they do from Southern India, agree externally with the types of M. providens, and have similar short Nesokian skulls.
In Lower Bengal, there is a burrowing rat, a great pest in gardens, in which it constructs numerous tortuous passages, some comparatively superficial, and others at times very deep, and throws up heaps resembling mole hills. It is closely allied to Mus providens, but differs from it in its somewhat greater size, and in other slight details, afterwards to be noticed. This is the rat which Blyth incorrectly identified with Mus indicus, Geoff., and with which he also wrongly identified Arvicola indica, Mus huttoni, Blyth, M. rattoides, Hodgson, Mus pyctoris, Hodgson, and Mus dubius, Kelaart, but which is perfectly distinct from Mus (Nesokia) hardwickii which also differs from M. huttoni. It appears probable that this is the rat also figured in the Ill. Ind. Zool. Vol. II, pl. 21, under the name of Arvicola bengalensis, but which was never described. This being the case, the Bengal form must be named, whilst Mus (N.) hardwickii will stand for the rat originally described as Arvicola indica, and afterwards as Nesokia hardwickii; the original of the figure of A. indica being probably the type itself of Mus hardwickii, whereas M. (N.) providens will stand for the Southern form first described by Gray under the barbarous name of M. kok. In the Indian Museum, there are many rats in alcohol from Fateh
* Abhand. der K. Akad. Wissensch. zu Berlin, 1840, p. 143, Taf. II, fig. 1.
I may take the opportunity to record here that males and females of this rat escaped from confinement in the Calcutta Museum.