192 MOLLUSCA FROM THE CRAG. 
ceding species (a shell to which it seems nearest related)-in several characters, being 
smaller, and the ridges have an oblique direction, or they are subconcentric, deviating 
a little from the lines of growth, so that two or three only are lost in the centre of the 
ventral margin, and in some specimens, more especially in those which are longer than 
high, this character is less distinct than in those which are more orbicular, or have a 
greater comparative height, where this running out of the ridges at the margin is most 
conspicuous. The form of the shell resembles that of 4. digitaria, but the sculpture is 
different, and the margin in this, when it has attained full maturity, is furnished with 
rather large crenulations. In 4. digitaria the ridges are broader and flatter than in this 
species, in which they are somewhat rounded. The dental characters are those of a 
true Astarte, having one triangularly-formed cardinal tooth in the right valve and 
two in the left, while the most conspicuous lateral tooth, or where there is a depres- 
sion for the elevated edge of the opposite valve, is on the anterior side in the right 
valve, and on the posterior side in the left; the muscle marks also correspond with the 
generic character. 
Some specimens of this species have also the remains of coloured bands. 
20. AsTARTE PaRvA, S. Wood. Tab. XVII, fig. 12 ad. 
AsTarTE PARVA. SS. Wood. Catalogue Mag. Nat. Hist., p. 249, 1840. 
Spec. Char. Testd parvd, ovatd, transversd, valde inequilateral, postice breviore, 
antice productd, rotundatd ; striata, striis obliquis; umbonibus acutis, prominulis; margine 
integerrimo. 
Shell small, ovate, transverse, very inequilateral; posterior side the shorter, 
anterior much produced and rounded, ornamented with oblique transverse ridges not 
parallel to the margin; umbones sharp, somewhat prominent, and margin smooth. 
Length, 4th of an inch; height, a little less. 
Localities. Cor. Crag, Sutton. n 
The sculpture differs materially in the direction the lines take im crossing the 
exterior from that of the preceding species, which deviate a little from the lines of 
growth, there being more of them upon the anterior or larger side than there are 
upon the posterior side, three or four running out at different parts of the margin, 
so that, counting from the umbo, they number more towards the anterior than 
on the other side; the ridges are broad and flat, separated by a depressed furrow, 
much narrower than the ridges, about 12 or 15 on the posterior side, with 15 to 
18 upon the anterior, while the umbo or very young shell appears to have been quite 
smooth. The dental characters are those of true Asfarte, with one large triangularly- 
shaped tooth in the right valve, and a distinct, elongated, anterior, lateral tooth at some 
distance ; and in the left valve are two diverging cardinal teeth, with a duplicature or 
lateral tooth on the posterior margin; there is a somewhat thickened ridge on the 
posterior side, as in most of the species of this genus, within or behind which is the 
