Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/93

 AND AYES OF NORTII AMERICA. 87 Iguanodon and lladrosaurus there is a very small sphaoroicl condyle on the inner side of a broad proximal extremity. If the condyle only articulated with the scapula, the iota-fion of the humerus would be 'very limited; if the long narrow proximal articular surface, which is the whole of the flattened proximal extremity of this bone the rotation would be still less. In Laelaps how ever I find no round condyle; only the long narrow articular face of the proximal extremity, as in the Crocodiles. This would not allow of abduction and adduction, but as in the bird., of only flexure and extension. This is readily seen in the movements of the Crocodile. I suppose the anterior limbs were more useful as sup-ports when these animals placed the head near the ground, than for any other purpose, especially in Laelaps and its allies. The character of the articulation of the vertebral column by intervertebral discs, the double headed ribs, the elongate sacrum and large medullary cavities of the long bones have been cited by Prof. Owen in evidence of the Mammalian tendencies of the animals of this subclass. Their reptilian features, the single occipital condyle, quadrate and coracoid bones, with the median tarsal ginglymus, are equally shared by the Axes, though most of the usual distinctions between the latter class and the Reptiles hold good here also. Prof Owen also points out a special bird-like tendency in the alternation instead of superposition of the neural arches of the sacium on their contra, and other points can can now be added. Thus the reduction of the metatarsals to three in some of the genera, and their close approximation and excess of length over the phalanges, brings to mind these bones in the penguin. With the same reduction follows the confluence of the first series of the tarsal hones, and the great diminution of strength of the fibula and its close application to the tibia; the front limbs are much reduced, and the long bones more pneu-matic. In the most extreme form in this direction known, the first series of tarsal bones is entirely confluent with the tibia as in the birds, the three metatarsals are much elon-gate, the cervical vertebrae increase in number, and the pubes assume a position at right angles to the vertebral axis, which is intermediate between their anterior position in most Reptiles, and their posterior, in Birds. These features indicate three perhaps suborders, which are defined below. Quite as important, as indicating the urine affinity and remarkable character of this order, is the evidence derived from the pelvis. And first, the support of this arch, the femur, has been already alluded to. The head and neck of this bone are at right angles to the direction of the condyle. In other reptiles the axes of these are oblique to each other, so that the femur does not move in the direction of the axis of the body, but obliquely to it, thus permitting the body to rest on the earth. In the present case the structure is the same as in the birds and Mammals; the femur could only move in a plane parallel with the axis of the body. The reduced length of the fore limbs of many Dino-