/ 
161 
DENTALIUM decussatum. 
TAB. L XX.— Fig. 5 . 
Spec. Char. Surface marked with twenty or more 
longitudinal stride and several intervening ob- 
scure ones; lines of growth numerous, distinct, 
oblique; mouth elliptical. 
The longitudinal striae are much more numerous in this 
than in the last, but not much more prominent, although 
the shell' is nearly twice the diameter; they are decussated 
by the lines of growth, the obliquity of which seem to 
indicate an elliptic mouth. 
I received this specimen from the great Friend to Botany 
and science, William Borrer, Esq. from Sussex* 
DENTALIUM ellipticum. 
TAB. L XX.— Figs. 6 and 7. 
Spec. Char. Nearly straight, quickly tapering, 
rather compressed, surface uneven, aperture 
circular; external edge elliptical. 
The shell being thicker along two sides, gives the tube a 
depressed form, and makes the outer margin of the mouth 
elliptic; the lines of growth give the surface a rugged 
aspect; internally it is beautifully polished: the diameter 
of the mouth is sometimes nearly half an inch. 
This is a large species, apparently not before noticed, for 
want of better specimens ; it is however the more deserving 
