80 MR. KE. T. BENNETT ON THE GENUS OCTODON. 
Octodon. Ctenomys. 
In. In. 
Greatest. breadth.of, dittomy-y) ota nina a ae) ee 3 
Length of the lower jaw, (including the teeth) . . . . 13? 15 
Height of the.coronoid process.) }) 4-0-2 3) 4 SP 5 
Having thus adverted to some of the more interesting points in the consideration of 
these animals conjointly, I now proceed to describe individually the two that are con- 
tained in the Society’s Museum. For the third, to the most important distinctive cha- 
racters of which I have already alluded while comparing it with the others, I cannot do 
better than refer to the paper of M. F. Cuvier previously quoted, in which all the neces- 
sary details respecting it will be found. That able zoologist possessed the opportunity 
of inspecting the viscera of Poephagomys, the only one of the three genera that has yet 
been anatomically examined ; and by his sketch, as well as by his description, it appears 
that the intestinal canal is lengthened, as is usual in herbivorous animals, and that the 
cecum, as is also generally the case in such animals, is of considerable dimensions: in 
length it exceeds the stomach, is not greatly inferior to it in circumference at its larger 
end, and rapidly tapers towards the opposite extremity into a point’. 
Fam. ARvICOLIDz ? 
Genus Ocropon. 
Dentes primores 2, acutati, anticé leves: molares utrinque utrinsecus +, complicati, sub- 
zquales ; superiores subtransversi, facie antica lata, postica (ob incisuram externam 
profundam) duplo angustiore, interna in medio uniplicata, plicis a primo ad postre- 
mum sensim minoribus ; inferiores obliqui, singulo plica externa internaque sub- 
oppositis coronidem in areas duas obliqué transversales, figuram 8 vel clepsydram 
quodammodo simulantes, subdispartientibus, plicd externa in postremo vix con- 
spicua. 
' Since the above was written, the Octodon which was then living in the Society’s collection has died: but, 
by some oversight, I was not informed of the occurrence until long after it had taken place; and the oppor- 
tunity of anatomically examining the animal was consequently lost to me. From Mr. Martin’s notes of the 
dissection, however, I learn that the cecum was very capacious, and measured in length more than the sto- 
mach, the length of the one being 3, and of the other 2, inches ; and that it was sacculated ; its precise form, 
however, could not be ascertained, the ulceration which had taken place in it having prevented its distension ; 
that the stomach was of a regular, nearly oval shape, equally rounded at both extremities: and that the small 
intestines measured 2 feet 6 inches in length, and the large intestines 1 foot 6 inches; making a total length of 
4 feet, and being about seven times the length of the body: and that the commencement of the colon was dis- 
posed in a long loop or fold, its latter portion, with the remainder of the large intestines, scarcely equalling in 
diameter the small intestines. In all these particulars the alimentary canal of Octodon, like that of Poepha- 
gomys, accords with the general structure of the same part in other Herbivorous Rodents. 
The details of Mr. Martin’s dissection will be found in the Proceedings of the Society for July, 1836. 
