But one species of Camarasaurus has as yet been discovered. This I have named C. supremus, in allusion to its huge size. The bones, so far discovered by Mr. Lucas, are: a cervical and twenty dorsal and lumbar vertebræ, with twenty caudals. Both scapulæ and coracoids were recovered, with one-half of the sacrum, and two pairs of pelvic bones. Of the hind limb I have the femur, with Figs. 11, 12--Pelvic bones of Camarasaurus supremus. a tibia less certainly belonging to the same animal, although found among the other bones. There is one metapodial. There are many other bones which I have not yet reconstructed or determined. The dimensions of this animal may be inferred from the fact that the cervical vertebra is twenty inches in length and twelve in transverse diameter; and that one of the dorsals measures three and a half feet in the spread of its diapophyses, two and a half feet in elevation, and the centrum thirteen inches in transverse diameter. Another dorsal is two feet ten inches in elevation. The femur already mentioned is six feet, and the scapula five Fig. 13-Dorsal vertebra of Amphicalias altus seen from behind, exhibiting the hyposphen. Fig. 14--The vertebra represented in Fig. 13 seen from the right side, displaying the excavations of the neural arch and spine, and the pneumatic foramen of the centrum. and a half feet in length. The posterior dorsal vertebræ exceed in dimensions those of any known saurian, equaling those of the right whale. The centra measure sixteen inches in transverse diameter. The neck was probably ten feet in length. That this species was capable of and accustomed to progression on land, is certain from the characters of the bones of the limbs and their supports above described. The extraordinary provision for lightening the weight of a portion of the skeleton has more than one significance. It must be borne in mind that the caudal vertebræ retain the solid character seen in those genera which stood habitually on their hind limbs. That the present species was herbivorous is suggested simply by its huge dimensions, and the natural difficulty of supplying itself with animal food. The scapula is enormous as compared with the pelvic bones. The sacrum is also small and short, showing that the weight was not borne on the hinder limbs. The great length of the humerus in the probably allied genus Dystrophæus, from the Trias of Utah, adds to the probability that the same bones were large in Camarasaurus. This character, taken in connection with the remarkably long neck possessed by that genus, suggests a resemblance in form and habits between those huge reptiles and the giraffe. While some of the later Dinosauria elevated themselves on their hind limbs to reach the tree-tops on which they fed, the general form of the body in some of these earlier types enabled them to reach their food without the anterior limbs leaving the earth. The vertebræ from all parts of the column of Camarasaurus are known, and those of the dorsal and lumbar regions present the extraordinary character, of which a trace is seen in Cetiosaurus, of neural spines expanded transversely to the axis of the column. Numerous vertebræ of Amphicælias are known, and in the dorsals in which the neural spine is preserved, the latter displays the usual form, that is, it is compressed in the direction of the axis of the column. The centra differ from those of Camarasaurus in the form of their articular extremities, resembling more nearly in this respect the genus Tichosteus Cope (Palæontological Bulletin, No. 26, p. 194). They are unequally amphicœlous, the posterior extremity being more concave, and with prominent margins; while the opposite one is less expanded, and is but slightly concave. The neural arch is coössified to the centrum, and there is no capitular costal articulation on the latter. Fig. 15-Femur of Amphicalias altus, seen from the inner posterior direction. The lightness of construction of the vertebræ of this genus is as remarkable as in the Camarasaurus, but is differently exhibited. The greater fore and aft extent is seen in the fossæ, which are therefore not so deeply excavated as in that genus, but the osseous walls are not less lightened and attenuated. The elevation of the middle line of the back must have been extraordinary in the Amphicalias altus (Figs. 13, 14), and the huge knob at the summit of the neural spine indicates the strength of the longitudinal ligament which connected the vertebræ with each other and with the head. The femur of Amphicalias altus is remarkable for its slender form. It is a few inches longer than that of the Camarasaurus supremus, but is not so robust. The shaft is nearly round and somewhat contracted at the middle, where it is slightly convex backwards. It is slightly curved inwards at the great trochanter. Here the shaft is moderately grooved on the posterior face. This trochanter is only a prominent ledge below the head. The third trochanter is situated a little above the middle of the shaft; it is a prominent obtuse ridge directed backwards. The condyles are extended well posteriorly, and are separated by a deep popliteal groove, which originates on the |