o 
e 
TO GEOLOGY. 165 
MV. sulcatum. Plate 5. Fig. 168. 
Description. Shell turbinate, inflated, transversely fur- 
rowed over the whole surface ; substance of the shell 
rather thin ; transverse furrow linear with indistinct angu- 
; suture rather small ; whorls 
lar points ; spire : 
convex ; umbilicus none; mouth ovate, narrow ; columella 
smooth ; outer lip sharp. 
Length.... Breadth .2, ofan 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. 
