The estimate given by Marsh of the total length of this animal is nearly or quite 6o feet; the tail is figured at about 24 feet. Since the vertebra believed by Marsh to be the third caudal is probably the ioth or IxIth, the tail should be increased to over 30 feet in length, by the addition of at least seven large anterior caudals. The total number of caudals is estimated at 4o as against 37 in Di. plodocus. Marsh has attributed to Brontosaurus 27 precaudal vertebrae, or 13 cervicals and I4 dorso-lumbars. From reasons given below it is probable that there was a larger number of dorso-lumbars, which would still further increase the length of the animal to considerably over 6o feet. We can only conceive of the Camarasaur as a great wading and swimming quadruped, enjoying a habitat similar to that of the Upper St. John River, Florida, at the present time, namely, a relatively firm bottom gently graded to all depths, supporting a richly luxuriant aquatic vegetation, the river banks bordered by sloping shallows of sand (Colorado, Canon City Beds) or clays (Wyoming, Como Beds). As imagined by Cope in his picture of Amphica'iias ('Century Magazine,'November, I887), the animal could walk along the bottom, raising the anteriorportion of its body. We believe also that it could swim rapidly, propelled by its light but long and powerful tail, which would be useless upon land. The abundance of cartilage around all the limb joints and the non-osseous nature of many of thecarpals and tarsals afford positive evidence that the limbs were not con-tinuously subjected to the hard impact of the enormous weight of the body by motion on land. Feeding was done in the water and along the shores. Excursions upon shore were there-fore like those of the Alligator, mainly for breeding and egg-laying purposes, and they exposed the animal to attack by the Megalosaurs. By means of powerful mid-and posterior-dorsal spines and opisthocoelous vertebrae, the entire anterior part ofthe