ANATOMY OF THE BEAVER. 49 



The eyes are small, half an inch in diameter, and are 

 midway between the nostrils and the ears; diameter 

 of iris, 8'"; length of closed eyelid, 50'". A few bris- 

 tles over the eyes. The ears are short, very hairy on 

 both sides, rounded and obtusely pointed. The pos- 

 terior extremity of the beaver presents a singular 

 formation. The body diminishes in size gradually 

 from the hips, and terminates in a flat scaly tail, 

 which, measured from the sacrum, is about 18" in 

 length; the first 8" being covered with hair like the 

 rest of the body. The scaly portion commences ab- 

 ruptly with a width of about four inches, and termin- 

 ates with a rounded extremity. The scaly portion 

 (Plate II ) is slightly convex above and below, thin at 

 the margin, and is covered with a black, tough, scaly 

 ej^idermis. The scales are somewhat irregulnr in form 

 and size, the most usual form being sub-hexagonal, 

 about 32'" in length, and 12'" in width. They are 

 arranged transversely in respect to length, in the so- 

 called quincunx form, and they diminish in size to- 

 ward the end of the tail; across the middle of the tail 

 their number is 19 or 20 above, and 20 or 21 on the 

 under surface. A few short, broken hairs pass out 

 between the scales. 



It may be observed here that although this struc- 

 ture is usually described as scaly, it is so only in ap- 

 pearance. M. Sarrasin^escribes the "scales" as "cou- 

 chees les unes sur les autres, jointes ensemble par 

 une pellicule fort delicate, ench asses dans la peau dont 



^ Histoire de I'Academie Royale des Sciences. Annee 1704. 

 Paris, n45. Lettre de M. Sarrasin, medecin du Roy en Canada, 

 touchant I'Anatomie du Castor, p. 61. 



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