MR. E. T. BENNETT ON THE CHINCHILLID. 53 
to the intestines of the latter than either Mr. Yarrell or myself: it is probable that he 
took more pains in loosening them from the loops of peritoneum, for his accuracy of 
observation is beyond question. He describes the small intestines as measuring four 
feet six inches, and the large seven feet six inches, in length. On each side of the 
ileo-cecal valve, internally, he notices an oval patch of glandule aggregate, about two 
thirds of an inch in the long diameter. The cecum, he observes, is drawn up into 
sacculi by two longitudinal bands: these sacculi being directed alternately from right 
to left, and vice versd, give it at first the appearance of being spirally twisted, but on 
cutting across the longitudinal bands the sacculi fall down and the spiral character is 
lost. Connected with the extreme portion of the colon, he states that there is a lacteal 
gland of large size, with numerous lacteals evidently converging towards it; a circum- 
stance which, if further evidence were wanting, proves, he remarks, the share taken by 
the large intestines in the process of chylification. The trachea was composed of 
twenty-three imperfect rings ; the larynx formed two shallow sacculi ; and the epiglottis 
was small, with a truncated aper. Mr. Owen adds, that Meckel’s muscle was furnished, 
in its tendinous part, with a sesamoid cartilage. 
In the general character of the skeletons of the two animals there exists a remark- 
able conformity ; which admits, however, of very striking modifications, and particu- 
larly in the form of the cranium. The occipital ridge is scarcely at all visible in Chin- 
chilla, but is strongly marked and prominent in Lagotis ; the posterior boundary of the 
skull is consequently transversely truncate, or even retusely concave in the former, 
while in the latter it forms the convex segment of a circle. In Chinchilla the upper 
surface of the whole skull is remarkably flattened, and may be subdivided into three 
regularly graduated regions, the posterior of which, bounded anteriorly by the coronal 
suture, is nearly square in its outline; the middle or inter-orbital, formed wholly by 
the frontal bones, is a much narrower parallelogram, with the sides somewhat exca- 
vated ; and the anterior, curved a little downwards and forwards, and formed by the 
intermaxillary and nasal bones, is still narrower and more linear. In Lagotis the 
posterior part of the frontal and parietal bones is strongly arched, and the narrowing 
of the skull forwards is more gradual, the inter-orbital region being much broader in 
proportion: there is a deep depression between the fore part of the orbits, contrasting 
strongly with the posterior arching of the cranium; and the narrow and perfectly linear 
projection, formed by the nasal and intermaxillary bones, is nearly horizontal, having 
only a slight elevation near its middle and no downward curvature. The greater 
breadth of the inter-orbital portion is principally owing to the spreading out of the 
margins of the orbit, which also adds to the expanse of the zygomatic arch. In both 
animals the infra-orbital foramen on each side is of great magnitude, its vertical diameter 
equalling two thirds of that of the orbit. 
But perhaps the most striking feature in the skull of the Chinchilla is the extra- 
ordinary development of the tympanic cells, which occupy more than half of the 
