20 



Possibly earlier and unrecorded westward migrations of the brown 

 rat took place. A few years ago Professor Waile, the archeologist, 

 while making excavations at Cherchell on the coast of Algeria, dug 

 up the skull of a rat, which he stated was contemporary with the 

 Roman occupation of the country under the Caesars. The skull 

 had but one molar, much worn, but the cranial bones were intact, 

 and French zoologists pronounced the remains as undoubtedly those 

 of the "surmulot," or brown rat. a This shows that we have little 

 more than conjectures for the early history of this species. 



The brown rat is said to have first appeared in Paris in 1750. It 

 was brought to the United States, probably from England, about 

 the beginning of the Revolution, 1775. According to Audubon, it 

 was unknown on the Pacific coast of the United States in 1851; but 

 Dr. J. S. Newberry thought it must have arrived at San Diego, 

 Monterey, and San Francisco at a much earlier date. 6 Doctor Cooper 

 recorded its arrival at Fort Steilacoom, Washington, as occurring 

 about 1855. 



GENERAL DESCRIPTION. 



The brown rat differs considerably from the black rat and the roof 

 rat. It is larger, has a shorter head, a more obtuse muzzle, smaller 

 ears, and a relatively shorter and stouter tail. The general color is 

 grayish-brown above and whitish below. The over hairs of the upper 

 parts have black tips. The tail is usually shorter than the head and 

 body combined. The average measurements of adult specimens of 

 the brown rat in the Biological Survey collections are as follows: 

 Total length, 415 millimeters (16.3 inches); tail, 192 millimeters 

 (7.1 inches); hind foot, 43 millimeters (1.7 inches). This species 

 sometimes attains a total length of 19 to 20 inches, and has been 

 known to weigh 24 to 28 ounces and even more. The average 

 weight of an adult brown rat is considerably less than a pound. 



The black rat is less robust than the brown rat. It has a longer 

 head, a sharper muzzle, and larger and broader ears (fig. 3). The 

 tail is longer than the head and body combined. The fur is of a 

 sooty, or plumbeous black, color, paler on the underparts. It is 

 much softer and denser than that of the brown rat, and the mixture 

 of very dark and lighter over hairs gives it a peculiar shining appear- 

 ance. The average measurements of 20 apparently adult specimens 

 in the collection of the Biological Survey are as follows : Total length, 

 379 millimeters (14.9 inches); tail, 207.4 millimeters (8.1 inches); 

 hind foot, 35.8 millimeters (1.4 inches). 



a Comptes Rendus des Seances de L 'Academic des Sciences, Paris, vol. 110, p. 

 1031, 1893. 



&Pac. R. R. Reports, Vol. 0, Zoological Report, pt. 2, p. 60, 1857. 



