180 
like perfect Dentalia, more especially when separated or 
having fallen out, and may often be taken for the shells 
themselves. I received these long since by favour of the 
late Mr. Cunnington, and lately by the friendship of Mr. 
Holloway. 
Dr. Thompson, in his Annals of Philosophy, asks how 
the Fluor was dissolved from the Quartz in some Mineral 
veins; and may I not here ask what has become of the 
Carbonate of Lime or shelly matter? What solvent would 
take away the Lime and leave the cavities where the shells 
were, so perfectly clean, and apparently having no avenue 
for its escape? I have still more curious facts of this kind; 
they serve fo enliven the imagination, and heighten our 
admiration of Nature. 
DENTALIUM.  incrassatum. 
TAB. LXXIX.—Figs. 3 and 4. 
Spec. Cuar. Very taper, curved, smooth, swelled 
near the aperture; aperture round; lip sharp. 
Sonar in its proportions to D. planum, but much more 
swelled near the lip, and more curved. 
Found in single specimens, or in numbers clustered to- 
gether, as fig. 3, in hardened Clay at Highgate. Fig. 4 is 
a specimen of the same species with part of a small one at 
the small end, giving it the character of a jointed species: 
found in the dark Clay at Richmond, where the specimens 
were generally scattered. 
