The largest shell of this genus is Cucullcea crassatina ; a ventricose 
shell, of considerable thickness, three inches and a half in length, and 
four in width ; the external surface smooth, except from fine transverse 
stria;, marking the growth of the shell, and faint traces of longitudinal 
sulci. This shell is found in the neighbourhood of Beauvais, and is the 
only species mentioned by M. Lamarck. 
Among the beautiful fossils yielded by the Devonshire whetstone -pits, 
is a shell belonging to this genus, with specimens of which I have been 
kindly favoured by Mr. Cleeve. This shell, which, if it has not been 
already otherwise designated, may be named C. glabra, is a thick, ob- 
long, transverse shell, nearly smooth, being marked only by the fine 
transverse stria; formed by its growth. The beaks are separated by a 
large flat rhomboidal area, with markings, which, when the valves are 
united, assume a lozenge form. The line of the hinge is finely crenu- 
lated, as well as the three transverse teeth, which terminate the hinge 
at each end. Mr. Francis Crow, who, as has been mentioned, found, 
in a field at Favcrsham, a silicious specimen of Strombus pes pelicani , 
exactly agreeing with that which I had been favoured with from the 
Devonshire whetstone -pits, found, in the same spot, several silicious shells 
of this genus also. This coincidence deserves particular notice, since it 
points out a singular agreement in the strata. The shell of this genus 
found by Mr. Crow, though not unlike that of Devonshire in its general 
form, is specifically different. This shell, if not already named, might 
be designated as C. decussata. It is a thick oblong transverse shell, with 
flatfish longitudinal ridges, decussated by fine transverse striae. The area 
separating the beaks, large, with slightly undulating markings in the 
form of half a lozenge. The long line, as well as the transverse teeth 
of the hinge, which in the preceding species were crenulated, appear, 
in this, to have been smooth. Among the shells which I was favoured 
with by Mr. Crow, is a single valve, which, from its extraordinary thick- 
ness and great obliquity, I am disposed to consider as of different species 
from either of the preceding : it is, however, in a state which will not 
