OOLITIC FORMATIONS. 15 



determine the shape of the angular process. The result showed that the lower margin of 

 this process {a) was inflected, so as to render the outer surface convex, yet not in so great and 

 traceable a degree as in Bidelphys, Phascor/ale, and Basyurus. The outer surface of the 

 ramus presents no trace of the fissures or sutures which, in Lizards and other cold-blooded 

 Vertebrates, separate the angular, dentary, and other, in them, distinct elements of the 

 lower jaw.^ The broad and simple coronoid process (c) of the fossil shows the wide 

 concavity and the anterior marginal ridge, such as were deduced from the impressed matrix 

 in the second specimen qI Amphitherium ; the entire and prominent condyle (^) rises 

 somewhat higher above the level of the molar teeth than was indicated by its incomplete 

 remains in the former specimens, and the outer surface of the fore part of the present jaw 

 shows four or five small outlets of the dental canal, as in Myrmecohius. 



Species 2. — Amphitherium Broderipii, Owen. Plate I, figs. 25, 25a, 25b. 

 History of British Fossil Mammals and Birds, 8vo, 1846, p. 58, fig. 19. 



The fourth specimen of Amphitherium, discovered in the Oolitic slate at Stonesfield, 

 was obtained there by the Rev. H. Sykes, M.A., and was presented by him to the Museum 

 of the Philosophical Institution at York, where it is now preserved. It contributes as 

 much additional information in respect to the shape of the crowns of the teeth as the 

 third specimen had done in respect to that of the jaw-bone. It consists of the left ramus 

 of the jaw, and offers its inner surface to the observer. It presents at its anterior part the 

 sockets of three incisors and one canine, of small and nearly equal size ; then follow the 

 empty sockets of three small premolars, each with two fangs ; to these succeed three 

 larger premolars, in place, each having two fangs protruded to a certain extent from their 

 sockets. Each of these teeth shows a small anterior as well as posterior tubercle at the 

 base of the large middle cusp, and there is a slight ridge, or ' cingulum,' along the inner 

 side of the base of the hindmost of these premolars. The first true molar is wanting, the 

 next four have their crowns entire, the last is a little mutilated. The crowns of these 

 molars present a different form from that which might be inferred from the fractured 

 molars of the foregoing specimens, they are more compressed, and have not two cusps on 

 the same transverse line. Each presents a large middle cusp, with a smaller but well- 

 developed and pointed one, at the fore and back part of its base ; the ' cingulum,' a part 

 pecuHar to mammalian teeth, plainly traverses the inner side of the crown, where it deve- 

 lopes three small cusps, one at the base of the large external cusp, and the other two 

 forming the anterior and posterior extremities of the crown of the tooth. This form of 

 tooth is unknown in existing Mammalia, but is as well adapted for crushing the cases of 



1 'Owen, Anatomy of Vertebrates,' 8vo, vol. i, figures— 88 Arapaima, 91 Chelone, 92 Emys, 93 

 Crocodilus, 97 Python, 2/2 Cyclodus, &c. 



