BIVALVIA. Lise 
6. ASTARTE MUTABILIS, 8. Wood. Tab. XVI, fig. 1 a—A. 
AsTARTE MUTABILIS. S. Wood. Catalogue, 1840. 
— pranata. Nyst, (not Sowerby.) Rech. Coq. Foss. d’Any., p. 7, No. 23, 1835. 
= — Id. Coq. Foss. de Belg., p. 151, pl. vii, fig. 6 a—b, 1844. 
Spec. Char. Testé transversd, oblonga, subcordatd, crassd, inequilaterali, postice 
longiore, truncata ; natibus late sulcatis ; lunuld profunde excavata ; levigatd ; marginibus 
incrassatis, crenulatis. 
Shell transversely oblong, inequilateral, slightly heartshaped, thick and strong; 
posterior side the longer, and truncated; umbones broadly sulcated ; lunule smooth, 
and deeply excavated; margins thickened and crenulated. 
Length, 2 inches ; height, 15ths ditto. 
Localities. Cor. Crag, Ramsholt, Sudbourn, Gedgrave, Sutton. 
Red Crag, Sutton, Alderton, Baldersey. 
Mam. Crag, Bridlington, (Lechkendy.) 
This is one of our most changeable species in this variable genus, and the two 
forms that have been figured are the extremes of variation, fig. a, 4, being the most 
constant, may be described as the type of the species. The adult shell is particularly 
thick and strong, with the muscle marks deeply indented; the posterior one is large 
and nearly oval, the anterior one is rather less, and more straightened on the inner 
side, and immediately beneath the anterior lateral tooth is the third small muscular 
impression ; the line of the mantle indicates posteriorly the short siphons of the living 
animal; externally the shell is nearly smooth, except at the umbones, which are nearly 
flat in the adult shell, with about a dozen broad and deep furrows; the umbones are 
generally sharp, curving over a broad and deeply-excavated lunule, with a large and 
elongated corselet, both of which are quite naked or smooth; in the right valve the 
cardinal tooth is large and projecting, somewhat rugged at the sides, with the like 
striations upon the inner surfaces of the two teeth in the left valve; lateral teeth 
obsolete ; the ventral margin is nearly straight, and the posterior side somewhat 
quadrate. The margin of this species is quite smooth and sharp until it has attained 
its full size, when it becomes much thickened and deeply crenulated. Numerous 
specimens of the young shell may be obtained at Sutton, and I have traced them 
down to less than a line in diameter. 
Fig. 1 e,f is, I presume, only an aberrant form of this species; it was obtained at 
Bridlington by Mr. Leckenby, to whom I am indebted for permission to have it 
figured. 
