48 MOLLUSCA FROM THE CRAG. 
Our shell is not strictly ovate, but more of an oblong form, with the angles rounded 
Off; the sides being somewhat straight, or of very gentle curvature, it is tumid and 
thin; the whole of the ribs being visible on the inside, they occupy the centre of the 
shell, and are distributed over about half the surface, two or three of the middle ones 
being the most distinct, and these are more conspicuously so on the inside ; umbones 
prominent and divergent, leaving a wide ligamental area between them, thereby 
enabling the animal considerably to divaricate the valves ; coste obtusely angulated, 
rough, but not imbricated, showing distinct lines of growth; hinge-line straight ; 
cartilage pit concave, projecting inwardly, forming an angle of 90°, and occupying 
nearly half the ligamental area. The shell extends on each side of the umbo into 
what are called auricles, the greater part of which space is occupied by the ligament ; 
on the inside beneath these auricles the shell is thickened and strengthened by a 
prominent ridge, diverging from beneath the umbo towards the sides: in some speci- 
mens may be seen the impression of the large adductor muscle inclining towards the 
centre; my largest specimens do not exceed half an inch, measuring from the umbo 
to the ventral margin, and the transverse diameter about half that size. 
A specimen from the Aigean Sea was given to me by Professor E. Forbes, with the 
name of ZL. elongata, which so much resembles some of the Crag specimens (fig. 3, ¢), 
that I have introduced the name among the synonyma. In the Aigean shell, which 
was obtained from the depth of 100 fathoms, the costated striz are in number 
about 20, more distinct and distant on the centre or convex portion, and of course 
widest near the margin, not rounded but angulated ; while in the generality of speci- 
mens of subauriculata they are rounded, but the same characters of sharpened coste 
are visible in some of the Crag specimens, and there is not a distinction between the 
two sufficient, in my opinion, for specific separation ; probably with a large number of 
individuals of the A%gean shell, as much difference might be detected as is exhibited 
in my Crag specimens. 
Upon some of the smaller and most perfect specimens of this species from the 
Crag, may be observed a row of fine crenulations, occupying the entire edge of the 
hinge-line (fig. 3, 4), being a miniature representation of what has been considered a 
good generic character; these are, however, so small as to be of little service for the 
ordinary purposes in which the teeth or prominent portions of the shell about the 
hinge are employed by the animal. 
Lima ovata, 8. Wood. Tab. VII, fig. 5. 
Limatuta ovata. S. Wood. Mag. Nat. Hist., New Series, vol. iii, p. 235, pl. 3, fig. 5, 
1839. 
Spec. Char. Testa minutd, ovata, equilaterd, undiqué clausd, inflaté; in mediis 
costatis, utringue obsoletis, costis angulatis circa septem; cardine recto, foveo ligamenti 
trigond, concava. 
