566 OBSERVATIONS ON SOME SPECIES OF 
These three species occur on corallines, &c. in abundance 
on all parts of the coast. They are slightly translucent and 
glossy, when recent, but, like other shells, they become 
after death opake and dull by maceration. They seldom 
exceed the tenth of an inch in size. Their inhabitants are 
unknown. The Fl bicorne (including the V. perforatum as 
a synonyme) has never occurred to me. 
4. F. lacteum. Test. Brit. 522. 
This species differs so widely from the preceding ones 
in structure, as to justify us in considering it as the type 
of another genus. In these, the second chamber is placed 
at the end of the first, in such a manner as that its mouth 
has the same aspect as the base of the preceding one. The 
base of the third chamber, taking its rise from the mouth 
of the second, stretches along the remaining side of the 
first, and has its mouth formed so as to possess the same 
aspect. Thus the mouths of the chambers are placed al- 
ternately at the opposite ends of that line which is parallel 
with the direction of growth. In the V. lactea, on the other 
hand, the cells are arranged obliquely and alternately along 
an axisp with the mouths of all the chambers always having 
an aspect towards the same pole, as is represented at Plate 
XV. fig. 6. where Jc and I are representations of each side 
of the body, and m of the mouth. 
The chambers are ovate, and v/eli defined on one side ; 
but they appear less numerous and distinct on the other. 
The chambers become narrower towards the mouth, which 
is in the form of a small circular aperture. The whole shell 
is delicately transparent, with the inner walls of the cham- 
bers appearing as white veins. The specimen figured by 
Walker as Serpida tenuis omlis lavis (Test. Min. tab. 1 . 
f. 5.), is probably a young individual. I am, however, 
more disposed to refer the species before nie to the F. Jac- 
