TO GEOLOGY. 1G3 



M. sukatum. Plate 5. Fig. 1G8. 



Description. Shell turbinate, inflated, transversely fur 

 rowed over the whole surface ; substance of the shell 

 rather thin ; transverse furrow linear with indistinct angu 

 lar points ; spire ; suture rather small ; whorls , 



convex ; umbilicus none ; mouth ovate, narrow ; columella 

 smooth ; outer lip sharp. 

 Length .... Breadth .2, of an inch. 



Observations. A single specimen only, and that with a 

 fractured spire, has come into my possession. The descrip 

 tion is therefore imperfect. I am not satisfied that it is an 

 adult. It may be found to be a larger species than here 

 represented when more are procured, and then some of 

 the above characters may be found to differ. It most 

 resembles the last described. It is not so elongate a 

 shell, and the furrows distinguish it at once. In regard 

 to the horn I refer to the remarks on the pyruloides. 



The Monoceros has not heretofore been observed so low 

 in the series even as the lower Tertiary Beds. One species 

 only in a fossil state seems to have been noticed in Europe. 

 M. Deshayes mentions a single species and that in the 

 Pliocene of the Subappennines. It has not heretofore been 

 observed in the formations of this country. In M. Des- 

 hayes s Tables, six recent species only are given. My 

 cabinet has nine. 



