U2 MAMMALIA. 



Two species have been ascertained, both from South Africa. 



The Dormice and Graphyures compose the second and last division of the Sciuridce or Squirrel famikj. 

 We approximate to the Dormice, [but with questionable propriety],— 



The Echymyds (Echymys, Geof. ; Loncheres, Illig.), — 

 Which also have four grinders, but differently formed ; the superior consisting of two laminae bent like 

 a V, the inferior of one bent and one simple lamina. The fur of several species is rough, with inter- 

 mixed flattened spines or prickles. They inhabit America. One of them, 



The Golden-tailed Echymyd (Hystrix chrysuros, Schreb.), is more than double the size of the Brown Rat ; it is 

 a handsome animal, of a brown maroon-colour, the belly white, with a crest of elongated hairs and a longitudinal 

 white band on the head ; the tail long, and black, with its posterior half yellow. From Guiana. Another, 



The Red Echymyd (Eck. rufiis; the Spinous Rat of Azzara), of the size of a Rat, reddish-grey, with tail shorter 

 than the body, is found in Guiana, Brazil, and Paraguay. It excavates long subterraneous burrows. [These 

 species with hairy tails pertain to the Nelomys of M. Jourdan, who restricts the term Echymys to the following.] 



Others have merely the ordinary kind of hair, more or less rough. 



The most remarkable is Erh. dacti/liacus, Geoff., the Long-toed Echymyd, which is still larger than the Golden- 

 tailed species, and has the two middle toes of the fore-feet double the length of the lateral ones : its scaly tail is 

 longer than the bodv fur yellowish grey ; the hairs on the nose forming a crest directed in front. 



The Mus paradoxus, Thomas (Lin. Trans, xi., Heteromys, Lesson), apparently differs only from the Echymyds 

 in possessing cheek-pouches. However, not having seen its teeth, I cannot arrange it. 



[The Cercomyds (Cercomys, F. Cuv.) — 



Are closely related to the preceding, and have also four molars surrounded with enamel, which are 

 deeply indented internally, and inclose three insulated circlets of enamel near their external border: 

 their form is still more Rat-like, but with the profile of the visage arched ; there are no spines in the 

 fur, and the tail is '.Dug and scaly. 

 One species (C. braziliensis) is figured by M. F. Cuvier m his great work on Mammalia]. 



The Hydromyds (Hydromys, Geof.) — 



Are ; n many respects related to the Echymyds externally ; but they are distinguished from all other 



Rats by their hind-feet, two-thirds of which are palmated : their molars, also, two in number above 



and below, have a peculiar character in the crown, which is divided into obliquely quadrangular lobes. 



the summits of which are hollowed out like the bowl of a spoon. They are aquatic. 



Several have been sent to Europe from Van Diemen's Land, some with the belly white, others with a fulvous 

 belly, but all deep brown above, with a long tail which is black at the base, the distal half white. They are some- 

 times double the size of the Brown Rat. II. hydrogaster and II. leucogaster, Geof. [The former is variable, but 

 the latter notwithstanding appears to be another species.] 



The Houtias (Capromys, Desm.) — 

 Have four molars above and below, with flat crowns, the enamel of which is folded inward, so as to 

 form three re-entering angles on the external border, and only one on the internal side of those above, 

 and the inverse in the lower ones. Their tail is round, and slightly hairy. Like the Rats, they have 

 five toes to their hind feet, and four with the rudiment of a thumb to the anterior ; their form is that 

 of Rats as large as a Rabbit or Hare. 



Two [three] species are known [all from the West Indies], which, together with the Agoutis, formerly consti- 

 tuted the chief game of the indigenous inhabitants. Isodon pilorides, Say, refers to one of them. [They are 

 net distantly allied to the Porcupines. It is remarkable that these animals hold up their food (a fusiform root for 

 instance) with one foot only to the mouth, resting on the other three. They ascend bushes with facility.] 



The Rats, properly so called, (Mus, Cuv.), — 



Have three molars to each jaw, the anterior of which is the largest [and the posterior smallest], and the 

 crowns of which are divided into blunt tubercles, which, by attrition, acquire the form of a disc vari- 

 ously indented ; their tail is long and scaly. These animals are very annoying from their fecundity, 

 and the voracity with which they gnaw and devour substances of every kind. There are three species 

 very common in houses, namely, 

 The Common Mouse (M. muscuhus, Lin).— Known in all times and all places. 



