MR. E. T. BENNETT ON THE CHINCHILLIDA. 49 
its surface. It adheres to the skin with a tenacity which adds much to its value in a 
commercial and economical point of view, and would alone give it a commanding su- 
periority over that of the Lagotis. It has a similar dusky colour at the base, with short 
tips of greyish white, and with scarcely a shade of the yellowish brown tinge, except 
occasionally towards the haunches and on the croup, and then only very slightly 
marked. The under surface is mottled like the upper, but with a much greater pro- 
portion of white. On the under surface of the tail, the short adpressed hairs are of a 
dirty yellowish brown, while the much longer and more bristly hairs of the sides and 
upper surface are whitish at their base, brownish black from thence through the greater 
part of their length, and yellowish brown at the tip, with the exception of the tuft at 
the extremity, which appears of an almost uniform brownish black, the tips being less 
distinguishable in colour than in the rest. 
_ For the external characters of Lagostomus, as I have not at present the skin to refer 
to and neglected formerly to take notes of it, I must refer to the paper of MM. Isidore 
Geoffroy-Saint-Hilaire and Dessalines D’Orbigny fils, and to the work of M. Lesson 
before quoted. 
' It may be also proper to mention here the supposed second species of Chinchilla, de- 
scribed by M. Isidore Geoffroy-Saint-Hilaire, in the paper just referred to, from skins 
in the possession of some Parisian furriers, without legs, ears, or tail. This animal 
would appear, from the description there given, to be indeed nearly related to Chin- 
chilla, and even in some respects to approach my Lagotis. But the colours assigned 
to it (yellow tinged with greenish and slightly undulated with black above, and bright 
golden yellow shaded with reddish brown below,) are too strikingly different from those 
of Lagotis to admit of their being regarded as the same. It is further said that in the 
species in question, the Callomys aureus, Isid. G.-St.-Hil., the base of the fur is brown, 
while in Chinchilla it is dark grey. In Lagotis, on the contrary, the base of the fur is 
only a shade lighter than in the Chinchilla, and is of that peculiar hue which, from its 
near approach to black, without partaking of any decided colour, I have generally been 
in the habit of denominating dusky, or when deeper dusky black. It has not the 
slightest tendency towards brown. 
The anatomical examination of Lagotis and Chinchilla gave the following results. In 
both animals, on laying bare the face, Meckel’s muscle appeared very distinct from the 
masseter at its anterior termination, but was shown on further examination to be, as 
usual, only a developed portion of that muscle. The parotid gland extended in a flat- 
tened form along the neck ; the submaxillary was more compact. The digastric muscle 
was strong, and had a slightly tendinous appearance in the middle, where it was con- 
nected with the os hyoides. The sterno-mastoid and cleido-mastoid muscles were 
distinct ; and the interarticular cartilage between the clavicle and sternum was remark- 
ably long, although less so than in the Porcupine, measuring in Lagotis three eighths, 
in Chinchilla about one quarter, of an inch. The thyroid gland ascended on each side 
VOL, I. H 
