BIVALVIA. 177 
smooth. In the recent state it is covered with a thick, olivaceous, or dark coloured 
epidermis, and at the umbones the shell is often eroded; marks of erosion are visible 
also, more or less, in most of the fossils.* Old specimens are generally thickened 
within, showing deeply-indented muscle marks. There is a deeply-excavated lunule 
on the anterior side, and a corresponding slope on the posterior dorsal margin, with a 
prominent fulcrum for the ligament. 
It is said to be obtained in deep water in the British seas, though probably it had 
an extensive vertical range, being found as a fossil at Bramerton, in association with 
Littorina littorea, Mytilus edulis, and others that now inhabit very shallow water; and 
the fossil specimens are in that good state of preservation to justify the supposition 
that they had not been transported from any great distance. 
4, AsTARTE BAstTEROTH, Lajoukaire. Tab. XVII, fig. 2 a—d. 
AsTarTE Basrerotit. Lajonk. Not. Geol. eny. d’Anv. (Mém. de la Soc. d’ Hist. Nat. de Par.), 
t.i, p. 129, pl. vi, fig. 3 a—e, 1823. 
— Nyst. Rech. Coq. Foss. d’Anv., p. 7, No. 26, 1835. 
— — Id. Coq. Foss. de Belg., p. 151, pl. viii, fig. 4 a—e, 1844. 
— wnivma. J. Sow. Min. Conch., t. 521, fig. 2, 1826. 
— — S. Wood. Catalogue, 1840. 
CRassina NiTmDA. Desh. 2d edit. Lam., t. vi, p. 258, 1835. 
Dale, Hist. and Antiq. of Harwich, t. xi, figs. 12 and 14, 1730. 
Spee. Char. Testé transversd, ovato-trigonula, sublevigatd, anticé rotundatd, postice, 
subangulatd ; natibus tenui-sulcatis ; lunuld elongato-ovatd ; margine crenulato. 
Shell transverse, ovately triangular, nearly smooth, anterior side rounded, posterior 
subangulated; umbones finely sulcated; lunule elongate and smooth; margin cre- 
nulated. 
Length, \2ths of an inch; height, 13th ditto. 
Localities. Cor. Crag, Sutton, Ramsholt, Sudbourn, Gedgrave. 
Red Crag, Sutton, Bawdsey, Felixstow, Walton-on-the-Naze ? 
The most distinguishing character of this species is a set of fine concentric ridges 
covering the young shell, and occupying generally less than the fourth part of the 
diameter of the surface, or a little beyond the umbones of the adult, while all the other 
part is smooth, or at least with only visible lines of growth.t 
The general size of the most common form of the Suffolk shell is an inch in length 
and iths of an inch in height, and it has generally then a crenulated margin, but the 
other specimen figured (fig. 2c, d) measures as much as an inch and “ths in length, with 
an edge perfectly smooth; they are all rather compressed, and have a deep, elongated 
* A recent specimen in the possession of Mr. Lowry, with the specific name of Jactea attached, but 
which I believe to be only a var. of this species, is quite free from ridges about the umbo. 
+ The ridges upon the umbo of the Belgian shell are somewhat larger than those upon the British 
specimens, and may be considered a distinct variety. 
