Page:Principal Characters of American Jurassic Dinosaurs; Part VI, Restoration of Brontosaurus.pdf/2

82 and each foot-print must have been about a square yard in extent. The tail was large, and nearly all the bones solid.

The diminutive head will first attract attention, as it is smaller in proportion to the body than in any vertebrate hitherto known. The entire skull is less in diameter or actual weight than the fourth or fifth cervical vertebra.

A careful estimate of the size of Brontosaurus, as here restored, shows that when living the animal must have weighed more than twenty tons. The very small head and brain, and slender neural cord, indicate a stupid, slow moving reptile. The beast was wholly without offensive or defensive weapons, or dermal armature.

In habits, Brontosaurus was more or less amphibious, and its food was probably aquatic plants or other succulent vegetation. The remains are usually found in localities where the animals had evidently become mired.

Among the new points in the skull of the Sauropoda recently determined are the following:

In Morosaurus, the pituitary fossa is comparatively shallow, much like that in the crocodile, and many birds, being connected with the under surface of the skull by the two usual divergent foramina for the passage of the internal carotid arteries. In Apatosaurus, however, it is remarkably different. Here the fossa becomes enlarged into a vertical canal, which, expanding below, communicates by a wide transverse orifice with the pharyngeal cavity. The arterial foramina are here canals thinly covered over with bone, and open just within the rim of the lower orifice. The pituitary cavity itself has a firm smooth wall throughout. The openings are both transverse, and oval in shape. The upper one is eighteen by six millimeters in its diameters; the lower opening thirty by twelve.

This remarkable connection of the cerebral cavity with the alimentary canal is an embryonic character, and corresponds to the condition observed in the chick at the fifth day of incubation. This peculiar feature appears to be a family character of the Atlantosauridæ.

In two genera of the Sauropoda, (Morosaurus and Brontosaurus), and probably in all members of this order, there is a pair of small bones connected with the skull which have not hitherto been observed in any vertebrates. These bones, which may be called the post-occipital bones, were found in position in one specimen, and with the skull in several others. When in