166 MOLLUSCA FROM THE CRAG. 
the fossil from Angers is, in all probability, the same, as I have no doubt the one figured 
and described by M. Nyst (C. squamulosa) is no more than a variety of this Protean 
shell. The valves are always very thick and strong, ornamented with rounded 
radiating ribs; these are covered with more or less rugose lines of growth at all 
times, and in some well-preserved specimens large and elevated squamz may be 
observed at somewhat irregular distances; the spaces between the ribs, upon the 
centre and anterior part of the shell, are rather narrower than the ribs themselves, 
more especially on the posterior part, where they are also less elevated. The umbones 
are slightly involute, and have a small plain space or lunule immediately beneath them. 
The right valve has one large tooth sloping towards the posterior side, with the rudi- 
ments of a small one before it, near the umbo; in the left valve is a large depression 
for the tooth of the opposite one, and a thin, linear, compressed tooth, nearly parallel 
to the dorsal margin, with a small triangularly-formed cardinal tooth, that becomes 
obsolete in some specimens: these elongated teeth are marked with vertical strize like 
the lateral teeth in some species of Jactre, Cyrene, &c. 
In those species with a very transverse form of valve, the shell is generally more 
compressed, and vice versd, in the orbicular varieties it is more tumid ; deep impressions 
are left by the adductors, and the margin of the shell is indented by the elevation of 
the ribs; a small additional muscle mark is left upon the shell joing the anterior 
adductor, such as is common to most of the species of Asfarte and some of the 
Veneride, and the ligament was probably strong and powerful, as indicated by the 
fulcrum, and deeply impressed furrow on the outside. 
In all my specimens, notwithstanding its extreme range in variation in regard to 
form, from that which is truly orbicular and nearly equilateral, to those which are more 
especially transverse and very inequilateral, they invariably possess the character of 
being somewhat rounded at the posterior side, and never angulated, like Ch. antiquata, 
Linn. I am not sufficiently acquainted with the Italian fossils to say whether either of 
the shells figured by Brocchi could be united with the Crag shell, but those specimens 
I have seen appear to differ in being also less rounded on the posterior side, with a 
slight difference in the form of the ribs, and covered with more prominent scales. 
2 CarRpiTa scALARIS, Leathes’ MSS. Tab. XV, fig. 5. 
VENERICARDIA SCALARIS. J. Sowerby. Min. Conch., t. 490, fig. 3, 1825. 
— — Nyst. Rech. Coq. Prov. d’Anv., p. 12, No. 47, 1835. 
— a Potiez et Mich. Catal. des Moll. de Douai, p. 166, No. 19, 1844. 
CARDITA — Goldf. Pet. Germ., vol. ii, p. 188, t. 134, fig. 2a, 6. 
— — Ngst. Coq. Foss. de Belg., p. 213, pl. xvi, fig. 9 a, 6, d, 1844. 
Spec. Char. Testé orbiculato-triangulari, depressd ; costis 20—22 convexis, nodosis ; 
concentricé sulcatis ; umbonibus medianis. 
