184 



Geological Society :— 



subequal, compressed, transparent, with a recurved tip, which in the 

 inner teeth of the series is bifid. 



•L 5 





Teeth of Ceres Salleana. 



1. Ceres Salleana, Gray. 



Shell yellow ; upper surface conical, convex, rugulose, with nu- 

 merous close, parallel, granular concentric strise ; lower surface 

 smooth, polished ; keel acute, expanded. 



Hab. Cordera, State of Vera Cruz, Mexico, in dense woods, under 

 dead leaves {M. A. Salle). 



2. Ceres eolina. Proserpina eolina, Duclos, Mag. Zool. 



The shell orange ; upper surface flat, rugulose, with numerous 

 short, parallel, diverging, narrow, sharp ridges ; keel very acute, bent 

 up ; lower surface convex, subhemispherical, polished, orange ; axial 

 callosity thin, semitransparent, whitish. 



GEOLOGICAL SOCIETY. 



January 7, 1857. — Colonel Portlock, R.E., President, in the Chair. 



The following communications were read : — 



1. " On the Dichodon cuspidatus." By Professor Owen, F.R.S., 

 F.G.S. 



In this paper additional facts were communicated relative to the 

 dentition of the Dichodon cnspidatus to those given in the author's 

 original memoir on the species in the ' Quarterly Journal of the Geo- 

 logical Society,' vol. iv. p. 36. They related to the structure of the 

 last molar tooth of the lower jaw, which has a third bicuspid lobe, 

 and to the forms and period of succession of the permanent teeth. 

 The formula of the deciduous dentition was 



dm 



4—4. 



that of the permanent dentition is 



= 32; 



3—3 



The form and structure of all the permanent teeth, with the excep- 

 tion of the fourth premolar, are now known. 



The deciduous formula is the same as in the genus Sus ; the per- 

 manent one differs by the displacement of the first deciduous molar 



