184 



Geological Societij : — 



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

 inner teeth of the series is bifid. 



/Or^/^i(j^; 



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 pa])er additional facts were communicated relative to the 

 dentition of the Dichodon cuspidatus 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 



;3-3 

 3—3' 



dm 



that of the permanent dentition is 



= 32; 



= 44. 



3—3 1 — 1 ■' 4—4 3—3 



I'he 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 



