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ceding species, is a little incurved and beak-formed; and its sinus, 
commencing at this beak, is smooth and rounded, like that Cuspidatus ; 
and joins with its base, at the back part, the base of the convex wave 
of the upper, or smaller valve, at a. 
I must acknowledge that the term foramen, or aperture, does not 
seem applicable to the triangular cavity in either of these shells ; it 
appearing to be rather a deep triangular groove, in which might have 
been fixed a strong muscle or elastic cartilage, the office of which might 
have been to have drawn open the valves. This, however, is only 
conjecture. I shall therefore proceed, acknowledging that I have dwelt 
longer on these two last species, from the expectation that it might 
lead to the better understanding of the following genus. 
CLIII. Calceolci. A regular inequivalved bivalve : the largest valve 
being in the shape of the pointed end of a slipper, and the small one 
flat and semicircular. The hinge with a central tooth, and four rugous 
projections at each end. 
This shell is very thick, and nearly an inch and a half in length. The 
back of the large valve is flat, and marked with transverse linear stria?, 
which are continued over the rounded fore part. The upper valve is 
striated concentrically. Plate XVI. Fig. 14, represents the upper, and 
Fig. 15, the lower valve of this shell. 
It is placed by Gmelin at the end of the genus Anomia, as Anomia 
sandalium. To this species, the only one which is known, Lamarck has 
given the name of C. sandalina. It was first discovered in the duchy of 
Juliers, by M. le Baron de Hupsch, of Cologne, who gave a particular 
description of it in a tract published at Francfort, in 1768, under the title 
of Nouvelles decouvertes faites dans Vhistoire naturelle de la basse 
Allemagne, des petrijications de quelques anbnaux testaces raves et peu 
connus , fyc. M. Hupsch kindly distributed these fossils among the more 
intelligent collectors, who were thereby enabled to form their respective 
opinions of these extraordinary bodies. M. Hupsch himself was of 
opinion that it was a fossil, inequivalved, bivalve shell, the smaller 
