100 
VENTRICULITES. 
directed blow on the margin, and very delicate 
casts and impressions may be thus obtained. 
The former exhibit the external integument 
changed into a white friable carbonate of lime ; 
the latter form conical cavities covered with nu- 
merous interrupted ridges, disposed in a radiated 
manner. 
The casts of the funnel-shaped cavity are solid 
cones ; their surface exhibiting numerous minute 
papillae that have been moulded in the open ex- 
tremities of the tubuli. A chalk specimen of this 
kind is figured by Lhwyd, No. I76.* : but it is 
drawn in an inverted position. 
VENTRICULITES RADIATUS, 
(Showing the formation of the siliceous specimens.) 
The fossil above represented is remarkably in- 
teresting, since it elucidates the formation of those 
* It is thus described : — “ Astroitm congener radulartn cretacea. E 
puteis cretaccis jnxta Aslon Rowanl in agro Oxoniensi.” — Lhwyd, 
Lilh. Brill. 
