BIVALVIA. 79 
and regularly decussated exterior, but with a small and narrow ligamental area. Arca 
nodulosa, Brocchi, seems to belong to our present species, as does also, in all probability, 
the one figured and described under that name by Dubois, judging from his short 
description and small figure. 
ARCA PECTUNCULOIDES, Scacchi. Tab. X, fig. 3, a—d. 
ARCA PECTUNCULOIDES. Sceac. Ann. Civ. delle Due Sicil., vol. vi, p. 82, 1834, fide Nyst. 
— — Scacchi. Notizia, p. 25, t. 1, fig. 12, sec. Phil. 
= a Phil. En. Moll. Sic., vol. ii, p. 44, t. 15, fig. 3, 1844. 
— —_ Jeff. Ann. Nat. Hist., vol. xix, p. 313. 
ee —_ Lovén. Ind. Moll. Scand., p. 34, 1846. 
— — ? Mich. Prec. Faun. Mioc., t. 3, fig. 14, 1847. 
— — Sismonda. Syn. Meth. Pedm. Foss., p. 16, 1847. 
= —— Nyst. Tab. Synop. des Arches Viv. et Foss., p. 54, No. 300, 1847. 
— RaripentaTa. S. Wood. Mag. Nat. Hist., New Series, vol. iv, p. 232, pl. 13, 
fig. 4, 1840. 
— —_ Thompson. Ann. Nat. Hist., vol. xviii, p. 385. 
— — S. Wood. Catalogue, 1840. 
_— — Morris. Cat. Brit. Foss., p. 78, 1843. 
— — For. and Hanl. Hist. Brit. Moll., vol. ii, p. 241, pl. 45, fig. 8, 
1849. 
—  pusitta. Myst. Coq. Foss. de Belg., p. 261, pl. 20, fig. 6, 1844. 
CucuLi@a pusILLa. Nyst. Rect. Coq. Foss. Prov. d’Anv., p. 14, pl. 3, fig. 55, 1835. 
Spec. Char. Testd parva, inequilaterd, ovato-rhomboided, gibbd; striis exiguis, 
decussatis; ared ligamenti parvd, apicibus reflexis ; cardine recto, utrinque tridentato ; 
margine ventrali subsinuato. 
Shell small, inequilateral, ovato-rhomboidal, gibbous; ornamented with fine 
decussating striz; ligamental area small, umbones inflected; hinge line straight, 
furnished with three teeth on each side; ventral margin subsinuated. 
Largest diameter, \th of an inch. 
Locality. Cor. Crag, Sutton. — Recent, Britain, Mediterranean, and Agean Seas. 
This elegant little shell is another species, but rarely found in the British Seas, and 
which may perhaps be one of those we might consider to be in a specific decline, or 
the dying out of what was once largely developed in these latitudes. In the Coralline 
Crag at Sutton this is one of the most abundant fossils, and I have obtained the 
separated valves by hundreds. 
It is stated by the authors of the ‘ Hist. of Brit. Moll.’ to be slightly inequivalved. 
In the fossil state I have never been able to obtain a specimen with the valves united. 
There does not appear to be any doubt of its identity with the living British species, 
and a single valve obtained from a considerable depth in the Hgean Sea, obligingly 
given to me by Professor E. Forbes, corresponds in all respects with the Crag shell. 
Where the specimens are so abundant, differences of form may naturally be 
expected, some may be selected that are more elongated and less tumid than others, 
