BIVALVIA. 261 
pubescens, \ have followed their example, although the characters for specific separation 
are not clearly defined,—the distinction appearing to rest solely upon one being more 
transverse than the other. There is, I think, little doubt but the so-called two species 
lived in the sea that deposited the Coralline Crag. 
Two or three fragments of what may be this species, or the young of the preceding, 
are in my cabinet, from the Red Crag of Sutton; and a specimen belonging to this 
transverse form is in the cabinet of Mr. Morris, from Uddevalla. 
Thracia detruncata, of my ‘Catalogue’ (fig. 1, e), is probably only a distorted 
specimen of a young individual of either this or of the preceding species. 
The umbo is cleft by the ligament, which must have been visible when the valves 
were closed. 
3. Turacta tnFLata, J. Sowerby. Tab. XXVI, fig. 6, a—e. 
Turacta conyexa.? S. Wood. Catalogue, 1840. 
— INFLATA. J. Sow. Min. Conch., t. 631, figs. 2—4, 1845. 
— Conrapt.? Couth. Bost. Journ. Nat. Hist., vol. ii, p- 153, pl. 4, fig. 2, 1839. 
Spec. Char. Testd obovatd, convexa, inflatd, sublevigatd, tenui, fragili; antice 
rotundatd, postice subtruncatd et angulatd ; margine ventrali arcuato. 
Shell obovate, convex, tumid, nearly smooth, thin and fragile; anterior side 
rounded, posterior angulated and pointed ; ventral margin curved. 
Length, 34 inches. Height, 23 inches. 
Locality. Cor. Crag, Sudbourn. 
This species appears to be restricted to the neighbourhood of Orford, where it is not 
at all scarce, though the specimens are rarely in perfect condition: they are generally 
more or less compressed, and the inflated character destroyed. Amongst my specimens 
a considerable variation may be observed, some being much more elongated than 
others. 
The right is the thinner and more inflated valve, and the one that is generally 
fractured and compressed. Impressions by the adductors are unequal in size, and the 
sinus in the mantle-mark is rounded and rather deep. A small sinus is visible at the 
umbones, through which the ligament must have protruded; but that part of the shell 
being particularly thin, it is there generally destroyed or injured. The hinge is an 
elongated callosity, on which was placed the cartilage, with a linear depression or 
furrow on the outside of it for the ligamental portion, differing from that of 7: pubescens, 
in which this callus is of a triangular form and projects inwardly. The exterior is 
smooth, with the exception of lines of growth and some rugosities, particularly upon 
the siphonal side; but it has not the shagreen-like sculpture which ornaments the 
entire surface of 7. pubescens. 
