150 Geological Society. 



interspace nearly equal to the antero-posterior diameter of the first 

 molar. The second and remaining molars are in close juxtaposition. 

 The third and fourth molars form the principal difference between 

 the dentition of the present genus and that of the Chasropotamus, 

 being larger and more complex in the grinding surface. They 

 present a sudden increase in size and change of form. The 

 plane of the crown is triangular, with the base outwards, and the 

 posterior and inner side convex : it supports three principal cusps, 

 two on the outer, and one on the inner side ; there are also two 

 smaller elevations with a depression on the summit of each, situated 

 in the middle of the crown, and the whole is surrounded with a ridge 

 which is developed into a small cusp at the anterior and external 

 angle of the tooth. The three true molars closely correspond with 

 those of the Chseropotamus. The sockets of the canines indicate 

 that these teeth were relatively as large as in the peccari. 



The bones of the head are separately described : the palatal 

 processes of the maxillary bones are shown to be rugous, as in the 

 peccari ; the eye to have been full and large, as indicated by the size 

 of the optic foramen and the capacity of the orbit, equalling an inch 

 in vertical diameter : the general form of the skull is described as 

 partaking of a character intermediate between that of the hog and 

 the hyrax, though the large size of the eye must have given to the 

 physiognomy of the living animal a resemblance to that of the Ro- 

 dentia. 



These indications, Mr. Owen says, scanty though they be, of the 

 form of a species nearly allied to the Chseropotamus, are extremely 

 interesting, on account of the absence of similar information regard- 

 ing that genus. The resemblance of the molar division of the 

 dental system in the new genus, for which the name of Hyracothe- 

 rium is proposed, and the Chseropotamus, is sufficiently close to 

 warrant the conclusion, that the canines and incisors if not similar 

 would differ only in form and proportion ; and that hence it may be 

 ventured to solve analogically some of the doubts entertained by 

 Cuvier respecting the dental characters of the Chseropotamus, and 

 to affirm confidently that it had canines in the upper as well as the 

 lower jaw. The incisor teeth with the ossa intermaxillaria are 

 wanting in the specimen of the Hyracotherium, and have not been 

 found in any fragment of the Chseropotamus. 



2. The remains of birds described in the paper consist of a sternum, 

 with other bones, and a sacrum, the former belonging to the collec- 

 tion of the late John Hunter, in the Royal College of Surgeons, 

 and the latter to the cabinet of Mr. Bowerbank. Both the speci- 

 mens were obtained from Sheppey. The Hunterian fossil includes 

 the sternum nearly entire, the proximal ends of the coracoid bones, 

 a dorsal vertebra, the distal end of the left femur, the proximal end 

 of the corresponding tibia, and a few fragments of ribs. Mr. Owen 

 first shows, in approximating to which of the three great groups of 

 birds, terrestrial, aerial, or aquatic, the Ornitholite belonged, that 

 from the length of the sternum and the remains of the primary in- 



