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 sub concentric, 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 A. digitaria, but the sculpture is 

 different, and the margin in this, when it has attained full maturity, is furnished with 

 rather large crenulations. In A. 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. XVIT, fig. \2ab. 



Astarte paeva. S. Wood. Catalogue Mag. Nat. Hist., p. 249, 1840. 



Spec. Char. Testa parvd, ovatd, transversa, valde incequilaterali, j}ostice hreviore, 

 antice productd, rotundatd ; striata, striis ohliquis; 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, ^th of an inch ; height, a little less. 



Localities. Cor. Crag, Sutton. 



The sculpture differs materially in the direction the lines take in 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 Astarte, 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 



