78 Description of the Bones of a new Fossil Animal. 



the base of which exists a foramen for the passage of vessels 

 and nerves, large enough to admit the end of the little finger, 

 into which, when at rest in an upright position, enters an angu- 

 lar projection formed at the outer and lower ridge of the socket. 

 This extraordinary construction of the ankle joint is altogether 

 proper to the animal under consideration, and which, whilst it 

 affords the strongest possible movable articulation, would neces- 

 sarily impede the hinge-like motion, in most animals very free 

 at this part ; and is confined principally to a semicircular and 

 horizontal motion, as in turning the toes outwards and inwards. 

 Plate I, fig. 15. The following are the dimensions of the tibia : 



Smallest specimen. Largest specimen. 



Total length, .... 10 inches, 1Q£ inches. 



Transverse diameter of the superior head, 5 T 3 a " 6 T \ " 



" " inferior head, 5 " 5J " > 



Circumference of middle of the shaft, 9 \ " 10 T 7 „ " 



Astragalus. — This is a large, irregular shaped bone, extensive- 

 ly marked with articulating surfaces, five in number ; two for the 

 tibia above, one below for the os calcis, and two anteriorly for 

 the other tarsal bones. The articulating surface for the os calcis 

 admits of a rocking or semi-ginglimus motion, in some degree 

 compensating for the absence of this motion in the ankle joint, 

 in which respect it differs from its congeners. Vide PI. I, fig. 16. 

 The dimensions of the astragalus are — 



Extreme breadth, . . . . , . 5 T \ inches. 



Height from the base of the bone to the top of the 



ovoid protuberance, ..... A r \ " 



To the base of the bone, . . . . 2 r % " 



Clavicle. — There are two or three pieces of bone resembling 

 portions of clavicle. The two pieces now under consideration 

 appear to have belonged to the smaller individual, and are the 

 sternal and scapular extremities, each about five inches in length, 

 two inches wide, and one fourth of an inch thick ; the bones are 

 of a strong structure, having but a slight development of cancelli 

 within. Yid. Plate I, figs. 17 and 18 — a transverse section. 



Ribs. — Of the several portions preserved, one only is nearly 

 perfect ; a considerable portion of this has been fractured, and 

 lost, from the sternal extremity. This piece is nearly two feet 

 long, two inches wide, and one inch thick ; the distance from 

 the centre of one spinal articulation to the other is four inches ; 



