426 Geological Society .•— • 



GEOLOGICAL SOCIETY. 



March 11, 1857. — Colonel Portlock, R.E., President, in the Chair. 



The following communications were read : — 



1. " On the Dichobune ovina, from the Upper Eocene of the Isle 

 of Wight." By Professor Owen, F.K.S., F.G.S. 



This paper comprised a detailed description of the lower jaw and 

 teeth of an Anoplotherioid quadruped (Dichobtine ovina, Owen), of 

 the size of the Xiphodon gracilis, Cuvier, and belonging to the family 

 that includes Dichobune and Xiphodon. The dental formula, as shown 

 by these teeth, and by the evidence on their crowns of the presence 

 of the teeth of the upper jaw, is the typical one in diphyodont 

 mammalia, viz. incis. g^, can. [^, premol. J^, molars, g^ = 44. 

 Professor Owen, having described the differences of the species 

 under notice from the allied species D. cervinum, concluded with 

 some remarks on the relations of the genera Xiphodon and Dichobune^ 

 as illustrated by their dental organs; and pointed out that the 

 small anoplotherioid Microtherium, so much in some respects re- 

 sembling the Chevrotains of Java, &c., but possessing persistent 

 upper incisor teeth, probably differed also from the Ruminants in 

 having a still more simplified structure of the stomach than is pre- 

 sented even by the Chevrotains {Tragulus, in which the third bag or 

 psalterium is suppressed) . Thus nearly all of the known eocene artio- 

 dactyle herbivores are separable from the Ruminants ; and of the very 

 few that remain, the dental evidences are as yet incomplete. Further, 

 the gradations of dentition displayed by the extinct even-toed 

 hoofed herbivores above referred to go far to establish the natural 

 character of the group Artiodactyla. 



2. " On two species of the fossil Mammalian genus Plagiaulax 

 from Purbeck." By Dr. H. Falconer, F.R.S., F.G.S. 



The author first alluded to the interesting relics of Mammalia 

 (^Spalacotherium) discovered some time since by Mr. W. R. Brodie, 

 in the cliflTs of Durdlestone Bay, near Swanage, and described by 

 Professor Owen in the Journal of the Society (vol. x. p. 420, &c.). 

 He then mentioned that Mr. Brodie had since made some important 

 additions to this Purbeck fauna (including the Triconodon) ; and 

 that Mr. S. H. Beckles had more recently obtained numerous addi- 

 tional evidences of mammalian animals (chiefly in the condition of 

 lower jaws), besides various valuable reptilian remains in the same 

 thin freshwater deposit which had yielded the fossil above referred 

 to, and was still energetically occupied in the research. Among 

 the specimens found by Mr. Beckles, are some portions of the 

 lower jaws of two species of a mammalian genus, which is best re- 

 presented among existing forms by the Hypsiprymnus or Kangaroo- 

 rat. Dr. Falconer names the fossil genus Plagiaulax, — an abbrevi- 

 ation for " Plagiaulacodon," from TrXaytos oblique, and avXai, groove', 

 having reference to the diagonal grooving of the premolar teeth. 

 "With regard to these two species (P. Becklesii and P. minor), 

 satisfactory evidence has been obtained as to the characters of the 



