TRANSACTIONS OP THE SKCTIONS. 73 



Cuvier, from the Upper Eocene marl at Binstead, Isle of Wight, Hampshire ; and 

 pointed out the characters by which it differed from the known nearest allied fossils. 

 The total length of the lower jaw was 5 inches 11 lines ; the extent of the molar series 

 of teeth 2 inches 11 lines, and that of the three true molars 1 inch Sj lines. 



The near equality in height of the crowns of all the teeth, and their general cha- 

 racter, show that the animal belonged to that group of the Anoplotherioid family which 

 includes the genera Dichohune and Xiphodon. 



It has the same dental formula as the Anoplotherioid and Anthracotherioid qua- 

 drupeds, viz. 



,-3-3 1-1 4-4 3-3 .. 



3-3' l-l' ^^4-4' 3-3 



It differs from the genus Dichodon in the absence of the accessory cusps on the 

 inner side of the base of the true molars, and both from Dichodon cuspidatus and 

 Xiphodon gracilis, in the minor antero-posterior extent of the premolar teeth : it cori-e- 

 sponds with the Dichohme leporinum, Cuv., in the proportions of the premolars and in 

 the separation of the canine and anterior premolar; and to this genus, therefore, the new 

 fossil was referred. Its size and proportions indicate its specific distinction from 

 previously defined species of Dichohune. The name proposed for this species is 

 Dichobune ovinum. The specimen forms part of the series of fossils in the British 

 Museum. 



On a Fossil Mammal (Stereognathus Ooliticus) from the Stonesfield Slate. 



By Professor Owen, F.R.S. 

 Prof. Owen exhibited, by favour of the Rev. J. P. B. Dennis, M. A., a portion of a 

 lower jaw, with three molar teeth, of a small mammal, from the oolitic slate of 

 Stonesfield, Oxfordshire, for which the name of Stereognathus Ooliticus had been 

 proposed ; and after a minute description of the characters of the bone and teeth, he 

 entered upon the question of its probable affinities. These could only be judged 

 of by the peculiarities of certain molar teeth of the lower jaw of the unique fossil. 

 Those teeth presented the singular complexity of six cusps or cones upon the grind- 

 ing surface, in three longitudinal pairs, the crown of the tooth being quadrate, broad- 

 est transversely, but very short or low. The jaw-bone presents a corresponding shal- 

 lowness and thickness. The cusps are sub-compressed : the outermost and innermost 

 of the three hinder ones are oblique, and converge towards the middle of the crown, 

 being overlapped by the outermost and innermost of the three front cones. The 

 three molar teeth occupy the extent of 4^ lines, or 1 centimetre ; each tooth being 3 

 millimetres in fore and aft extent, and nearly four millimetres in transverse extent. 

 After a comparison of these molars with the multicuspid teeth of the Rat, the Hedge- 

 hog, the Shrews and Galeopitheci, the author showed that the proportions, numbers, 

 and arrangement of the cusps in those Insectivora forbad a reference of the Stereo- 

 gnathus, on dental grounds, to that order. The same negative result followed a com- 

 parison of the fossil oolitic mammal with the sex-cuspid teeth with the eocene 

 Hyracothere, Microthere and Hyopotamus ; but in these the resemblance was 

 presented only by the teeth of the upper jaw. The lower molar teeth of the Choero- 

 potamus, to which the author deemed those of the Hyracotherium would most closely 

 approximate, when discovered, showed a rudiment of the intermediate cones between 

 the normal pairs of cones. The proportional size and regularity of the form of the 

 cones of the grinding teeth of the Stereognathus give a quite different character of 

 the crown from that of the multicuspid molars of the Insectivora, and cause the sex- 

 cuspid crown of the oolitic mammal to resemble the pente-cuspid and quadri-cuspid 

 molars of the before-cited extinct Artiodactyle genera. Prof. Owen concluded, there- 

 fore, that the Stereognathus was most probably a diminutive form of non-ruminant 

 Artiodactyle, of omnivorous habits. 



On the Scelidotherium leptocephalum, a Megatherioid Quadruped from 



La Plata. By Professor Owen, F.R.S. 

 The extinct species of large terrestrial sloth indicated by the above name, was first 

 made known by portions of its fossil skeleton having been discovered by Charles 



