THE BLACK OR SHIP RAT 589 



slightly shorter than 2 ; digits 3 and 4 are of about equal length and a 

 little longer than digit 2. There are five large and distinct pads, but 

 there is no free supplementary pad external to that at the base of 

 digit 5. In each foot the hallux reaches to the middle of the first joint 

 of digit 2 ; digit 5 is slightly longer, reaching the end of the first joint 

 of digit 4; digits 2, 3, and 4 are the longest of the toes, and nearly 

 equal to each other, 3 being the longest. There are six plantar 

 tubercles ; of these the postero-internal is more than twice as long as 

 broad, and it is wider in front than behind ; the postero-external pad 

 is well developed, and fully one-third of the size of that at the base of 

 digit 5 ; a small free supplementary pad is situated externally but close 

 to the pad at the base of digit 5, but no similar pad is normally present in 

 connection with the pad at the base of digit i. The skin between the pads 

 is wrinkled ; elsewhere it is smooth. The tail is long, its length usually 

 exceeding that of the head and body ; it tapers distally, is somewhat 

 square in transverse section and distinctly annulated throughout, there 

 being about nine of the scaly rings in a length of 10 mm. near the 

 middle ; it is clothed with short, stiff hairs both above and below, and 

 these rise from the distal edges of the scales. At the root of the tail 

 the hairs are sparsely distributed and very short, their length being 

 equal to the width of one annulation and a half only ; distally they 

 gradually become more numerous and longer, their length being equal 

 to the width of at least three annulations, and these latter they partially 

 or completely conceal. Posteriorly the hairs project slightly beyond 

 the tip of the tail, but they do not form a true pencil. The tail is 

 relatively longer in the young than in the adult ; it is composed of 

 thirty-seven or thirty-eight vertebrae (de I'lsle), and has from 250 to 

 260 annulations in all. There are ten mamms in the females, arranged 

 in two pectoral and three inguinal pairs. Occasionally supernumerary 

 mammae are developed in the pectoral region ; in some cases an 

 additional teat may be present externally to either the right or the 

 left anterior pectoral mamma; in others an additional pair may be 

 developed just in front of or just behind the normal posterior pectoral 

 pair. 



Pelage : — The longer whiskers are longer than the head and ears ; 

 the lower two or three are white, the others dusky. In addition two 

 or more long cilia usually rise from the supra-orbital region. 



The general covering of the body consists of three kinds of hairs 

 in all rats ; but these kinds intergrade with each other perfectly. Very 

 abundant and fine, unicoloured or annulated hairs, which attain a 

 length of about 7-5 mm., constitute the underfur. The middle hairs, 

 10 to 13 mm. long, are usually annulated, and the general coloration of 

 the animal is largely dependent upon the hue of their subterminal 

 bands; many of these hairs are coarse and grooved, and impart a 

 VOL. II. 2 P 2 



