Mr. Yarreil's Notes on Comparative A/iafomi/. 317 



the ccBcum f of an inch ; a large gland appears on each side of the ilium 

 at its insertion into the ccecum. 



Chinchilla.* \_Mus laniger, Molina. ? Cricetus laniger, Geoff.] 

 The head and skin only of this animal was submitted to examination. 

 The lateral and posterior bones of the head appeared to have been pecu- 

 liar in their form, but had suffered considerable injury, the upper surface 

 of the cranium was flattened, the zygoma bioad in front descending and 

 affording attachment to a strong flat tendon (independent of portions of 

 the masseter muscle) which appeared to have formed the anterior boun- 

 dary of a cheek pouch ; but these parts had also suffered mutilation. 

 The coronoid process small. Incisors f as usual in most rodent animals. 

 Molars *[* ; the three anterior molars of the upper jaw formed, of two 

 flattened parallel bony portions with three alternating lines of enamel : 

 the fourth molar possessed an additional portion of bone and enamel, but 

 smaller than the two principal ones; the direction of the parallel lamincB 

 of these teeth not at right angles with the Hne of the maxillary bone, 

 but inchning obliquely from without backwards ; the molars of the 

 lower jaw placed still more obliquely than those of the upper. 



The dentition of this animal does not agree with that of any genus of 

 Rodentia figured in the " Dents des Mammiferes'' of M. F. Cuvier. 

 The molar teeth of Lagomys are similar in structure, but are placed 

 directly across the line of each jaw bone. The recently described speci- 

 men of the new genus Lagostomus of Mr. Brookes, possesses the same 

 form and number of molar teeth, and their parallel lamince are placed in 



* A beautiful specimen of this species is now alive in the collection of the 

 Zoological Society, brought from Chili, and presented to the Society by Cap- 

 tain Beechey, R. N. We had intended to have given a figure of the animal, 

 and also plates of the system of dentition, in this number of the Journal, but 

 we are informed by one of our coadjutors, that we have been anticipated in 

 this object, and a plate of the Chinchilla has already been engraved in another 

 quarter. We know not the materials from which this latter plate has been 

 taken, as we have not heard of another living specimen besides our own hav- 

 ing ever been brought to Europe; but presuming on their being more perfect 

 than those we possess, (ours being very deficient as to internal strxicturej we 

 have laid aside our intention, at least, for the present.— Ed. 



Vol IV. Y 



