20 Memoirs of the Indian Museum. [Vol. I, 



brown, whereas in black rats it is dark greyish-brown or nearly black. The sole is 

 generally flesh-coloured but in a dark rat is slightly atreous, and in a black one dis- 

 tinctly so. The manus shows the usual five pads and a rudimentary tubercular 

 poUex bearing a nail. AU the other digits bear claws , which are white, hooked, and sharp . 

 The hind foot is long and narrow ; it shows the usual 6 plantar pads, the mesial ones 

 of which are markedly cordiform and generally show a supernumerary tubercle, as 

 is pictured in the foot of M. decumanus. 



Ears. — -The ears are very large, wide, and prominent, standing clearly out from the 

 head. They are scantily clad above with short, brown hairs, but below are nearly 

 naked. 



Mammœ. — Two pectoral pairs and three inguinal, with little tendency to vary. 



Habits. — The typical abiding place of Mus rattus is the thatch and crannies of 

 the roof, roof tiles, holes in the floor and such-like places. Unfortunately for it, the 

 structure of the average Calcutta house does not lend itself to providing such hiding 

 places, as the roofs are flat and built of masonry laid on beams, nowadays generally 

 of iron. In fact the modern house affords such a very small foot-hold to Mus rattus 

 that this may be the explanation of the comparative rarity of the species in Calcutta. 

 On the other hand, there are still large areas of tiled huts in the city. Though many 

 of the rats brought to me came from the upper stories of "pukka" (masonry) 

 houses, most came from huts, and generally from the cook-rooms of the huts. They 

 climb with great facility, scampering upside down along the wire roof of the large cage 

 in which I have some confined. Once or twice when in small cages, I have seen the tail 

 used as a support and point d'appui in climbing about. Twice I have had captured 

 rats litter immediately after being caught, and on each occasion the litter was three, 

 but 6 to 8 is the number normally found in pregnant females. At birth they are pink, 

 naked, with eyes and ears closed, and measure 5 cm., the tail being only 2 cm. long, less 

 than half the body-length. The tip of the ear conch is directed downwards and for- 

 wards under the skin. Even at the end of 10 days the conch is simply a little tag 

 with no external meatus. The meatus is represented by a small quadriradiate furrow. 

 I have now kept records of all rats found pregnant for a year from February to 

 February, and can state definitely that as far as observed in cities there is no breed- 

 ing season. At the Zoological Gardens they live to a great extent in the palm trees. 

 Mr. Sanyal, the Superintendent of the gardens, informs me that at one time he kept 

 rats taken from nests in the trees, and bred them in a masonry pit. He noted the 

 curious fact that in a few generations they lost their bright rufous colour and became 

 very dark brown, assimilating themselves to the ground in which they burrowed. 



Distribution.— Almost world-wide, doubtless from being introduced. Probably 

 indigenous in India and found throughout the country, also in Burma and Ceylon, 

 from the sea level to an elevation of at least 8,000 feet (after Blanford). 



Teeth. — It is rather difficult to describe the tooth of Mus rattus accurately, owing 

 to the impossibility of drawing a sharp line between what constitutes a rudimentary 

 cusp and what constitutes a rudimentary lamina. It may simplify matters to state 

 that the molars of this species consist of a varying number of sinuously-waved trans- 



