5 ZOOLOGICAL GARDENS. 
it had been previously placed ; and a closer examination 
served only to confirm the idea that it was equally 
distinct in character from every other known genus of 
Rodentia. In proof of the former part of this assertion 
we borrow from the Zoological Journal Mr, Yarrell’s 
description of these organs, taken from the specimen 
before-mentioned, with one indispensable alteration, of 
which that gentleman has himself since seen the neces- 
sity. He there describes the teeth as consisting of two 
incisors in each jaw, and of four molars on either side ; 
the three anterior of the upper jaw formed of two 
parallel bony portions with three alternating lmes of 
enamel, and the fourth having an additional portion of 
bone and enamel, but smaller than the two principal 
ones. The direction of the parallel lamime of these 
teeth is not at right angles with the line of the maxil- 
lary bone, but inclining obliquely from without back- 
wards; and the molars of the lower jaw are placed still 
more obliquely than those of the upper. 
But the examination on which this statement was 
founded was made under circumstances of great disad- 
vantage, inasmuch as it is almost impossible to obtain 
a distinct view of the teeth of any animal while the 
skull remains within the skin, from which it was of 
course not allowable in the present instance to remove 
it. The necessity for the alteration to which we have 
before alluded has been rendered obvious only since 
the skin was transferred to the British Museum, by 
the extraction from the lower jaw of the two anterior 
molars of the right side, which are now shown each to 
possess a smaller third lamina of bone, with its corres- 
ponding enamel, placed in front of, and not projecting 
so far externally as, the two remaining portions of the 
tooth. This third lamina is separated from that next 
to it by a deep groove on the inner side, but on the 
