NATURAL SCIENCES OF PHILADELPHIA. 237 



species or to A. firm u s. It exhibits a wedge for a diagonal gomphosis be- 

 tween the two sutures, which are preserved. The thickness on the median 

 suture is 14 lines. 



DINOSAURIA. ^ 



L.ELAPS Cope. 



L;elaps aquilunguis Cope. 



External J or 111 and position in Lfelaps. 



Tlie short fore-limbs of this genus suggest at once the habit qjt standing 

 upon the hind limbs chiefly, yet this disproportion is no sufficient reason 

 therefor, and is seen to exist in the tailless Batrachia, where no such position 

 is assumed. It exists to a less degree among the modern lizards, whose position 

 we well know to be always horizontal. 



Lfelaps had, however, no doubt an erect position, for the following reason : 

 The head and neck of the femur are at right angles to the direction of motion 

 on the condyles, or in the same plane as the transverse direction of the con- 

 dyles. This indicates that the femur has been reflexed and extended in a plane 

 parallel with that of the vertebral column. The relations of articulation are 

 those of birds, and different from those of reptiles, where the directions of the 

 proximal and distal condyles of the femur are oblique to each other, and the 

 proximal of a vertically elongate form, thus allowing the femur to be obliquely 

 directed as regards the axis of the body, so that in a prone position it rested on • 

 the ground equally clear of the body and the flexed tibia. 



The resemblance of the tibia, with its high crest and embracing astragalus, 

 as well as the slender fibula, to those of the birds, confirms this position ; so 

 do types of the iliac and sacral structures. The same is suggested by the great 

 bird-like reptile tracks found in many places. 



How must a reptilian form with elongate vertebral column and heavy tooth- 

 bearing cranium have stood erect? The elongate form of the femur as com- 

 pared 'with the tibia is only seen among animals who walk erect, in man ; in 

 the birds and kangaroos the femur is very much shorter than the t:'bia ; be- 

 sides these no other vertebrates progress on the hind limbs entirely. The 

 lizards, which are prone, present the long femur exceeding or equalling the 

 tibia. 



The bird-like reptile did not, however, exhibit the slight flexure between 

 femur and tibia presented bj- man. The acetabulum in the known Dinosaurs 

 is not or but weakly completed below, or what would be in man anteriorly, in- 

 dicating thatthe weight of the body was supported by a femur placed at a 

 strong angle with the longitudinal axis of the ilium ; otherwise the head of the 

 femur would be most readily displaced. If, therefore, the ilium were more or 

 less erect, the femur was directed forwards ; if horizontal, the femur must have 

 projected downwards. I have shown, however, that the position and therefore 

 the ilium was oblique or eject ; therefore the femur was directed very much 

 forwards.* 



There are, however, other reasons for believing that the femur was directed 

 forwards, and somewhat upwards from the ilium. One is, that the centre of 

 gravity of an elongate reptilian dorsal and sternal region must have been fur- 

 ther forwards than in the short-bodied bird, and therefore the knee must have 

 been further forward, in order to bring the support — i. e., the tibia, etc.— J3e- 

 neath it. Another is, that the articulation of the tarso-metatarsal bones with 

 / 



* The remarks of Prof.Owen on this relation in Megalosaurus are so pertinent, that they 

 are introduced here : 



"The backward position and production of the corresponding articular prominences or 

 condyles in both femur and tibia, indicate that these bones were joined together at an 

 angle, probably approaching a right one, when in their intermediate state between tlex on 

 and extension; and that the motion of the tibia could not have taken place to the extuat 

 required to bring the two bones to the same line." 



1868.] 



