BIVALVIA. 71 
In the young state the specimens have fewer teeth, and the shell, as before stated, 
is less oblique, resembling the young of Pectunculus, from which it may be distinguished 
by its smooth and acute margin at all ages ; while in the very small or young specimens 
of P. glycimeris the crenulated edge may be always seen. Some specimens are more 
tumid than others, but none are much inflated, and the exterior is smooth and perfect, 
except where it has been eroded, when the rays are more displayed, giving it there a 
granulated or decussated appearance, like Arca aurita of Brocchi, from which it appears 
to differ only in size. 
The remains of red-coloured bands may be seen upon some specimens as if the 
shell had been so ornamented when in a living state, or perhaps it was of one 
uniform colour, a part of which only has been abstracted. 
Trigonocelia Goldfussii, Nyst, from Kleyn Spauwen, much resembles our shell, but 
is probably specifically distinct; it has its margin obsoletely crenulated, and the 
denticles are more numerous, with a slight difference in their arrangement. 
Limopsis pyGMmA, Philippi. Tab. IX, fig. 3. 
Prctuncutus pyema@us. Phil. En. Moll. Sic. vol. i, p. 63, t. 5, fig. 5, 1836; not Lamarck. 
— — Id. - - - vol. u, p. 45, 1844. 
— —_— S. Wood. Mag. Nat. Hist., New Series, vol. iv, p. 234, pl. 13, 
fig. 5, 1840. 
—_— Td. Catalogue, 1840. 
—_ —_ Goldf. Pet. Germ. vol. ii, p. 162, t. 126, fig. 11, a—e. 
—_ — Morris. Cat. Brit. Foss., p. 97, 1843. 
Triconoc@ira pDEcUssATA. Nyst et West. Nouv. Rech. Coq. Foss. d’Anv., p. 12, No. 29, 
pl. 2, fig. 16, 1839. 
— — Nyst. Coq. Foss. de Belg., p. 245, pl. 18, fig. 7, a—d, 1844. 
Limopsis prema. Sism. Syn. Meth. Ped. Foss., p. 15, 1847. 
Spec. Char. Testdé minutd, obliqua, inequilaterd, subtrapeziformi, gibbosd, crassa, 
auriculatd ; transversim sulcatd, striis radiantibus tenuissimis, subobsoletis ; margine 
crenulato, dentibus circa decem. 
Shell small, oblique, inequilateral, subtrapeziform, gibbous, thick, and strong; 
hinge line straight, furnished with about ten teeth; externally covered with fine and 
nearly obsolete radiating strie, crossed by more distant and distinct lines of increase ; 
margin crenulated. 
Longest diameter, $ of an inch. 
Locality. Cor. Crag, Sutton. 
This species, as far as I know, is restricted to a single locality, where it is one of 
the most abundant shells, and the two valves are often found united. I have little 
doubt it is the same as Philippi’s Sicilian fossil, judging from the figure he has given ; 
the Belgian shell appears rather larger or badly represented, but from description it is 
probably the same. Our shell may be further described as being very tumid, the 
depth of the valves united equals the width of the hinge line; its dental formula 
