178 MOLLUSCA FROM THE CRAG. 



and smooth lunulc, and an elongated corselet on the posterior side ; there is an 

 elevated ridge of the dorsal margin in the right valve, and a correspondent furrow on 

 the same side in the left : the anterior lateral tooth or ridge is in the left valve, and 

 the corresponding furrow on that side in the right; there are three teeth in the right 

 valve, one large and two very small, with two large teeth in the left one ; the large 

 central triangularly-formed tooth is ridged or roughened on its sides, and the same 

 may be seen in perfect specimens on the inner side of the two diverging teeth of the 

 left valve. 



5. AsTARTE INCRASSATA? Brocchi. Tab. XVI, fig. 6r/ — b. 



Venus inck.\ss.\t.\. Broc Conch. Foss. Subap., p. yj/, t. xiv, fig. 7, 1814. 



Crassix.^ iNCR.iss.'^TA. Besh. 2d edit. Lam., t. vi, p. 25", 1835. 



AsTAitTE — Gohlf. Pet. Germ., vol. ii, p. 194, t. 135, fig. 2 a, b. 



— — P/(?7. En. Moll. Sic, vol. i, p. 38, vol. ii, p. 29. 



— NiTiDULA. S. Wood. Catalogue, 1840. 



Spec. Char. Testa crassd rotundato-triangulari, ttimiduld, subcEquilaterali, posticc paullo 

 lorif/iore, lavi, prcBterquam ad apices; lunula ovatd, profunda ; margine crenulaio. 



Shell thick, roundedly triangular, slightly inflated, subequilateral, posterior side 

 rather the longer ; smooth, except at the umboncs ; lunule ovate, and deep ; margin 

 crcnulated. 



Diameter, |ths of an inch. 



Localities. Cor. Crag, Sutton, Sudbourn. 



Red Crag, Sutton. • Recent, Mediterranean .- 



This species is abundant in the Coralline, and it is occasionally met with in the 

 Red Crag. Although sonicwh.-xt variable as a Hrilish fossil, it is less so than manv 

 other species of this genus. It most resembles the shorter varieties of the preceding, 

 but may be distinguished by several characters that apjjcar to be permanent. Our 

 Crag species has its identification in a Sicilian fossil, which is presumed to I)c the 

 same as Ast. incrassata, Phil., and V.incrassata, Broc, the former of these two authors 

 speaks of his shell as very variable in its external appearance, some, he says, arc almost 

 smooth, whilst others are sulcated almost to the margin ; our Crag specimens are 

 generally very regular in that character, and only in the region of the umbones is the 

 shell at all ridged, and these extend only to a short distance, while all the rest of the 

 surface is perfectly smooth. The shell as represented by Brocchi, is free from ridges 

 of any kind, although in the text, p. 557, he says, " natibus transversim rugosis." 



The general form of our shell is somewhat angulated or truncated at the posterior 

 side, the uml)ones turning a little towards the anterior one, over a large and deep 

 lunule, and on the other side is a large lanceolate corselet, witliin which is a con- 

 siderable space that was occupied by the ligament ; the umbonal region is occupied 

 by numerous small and rounded ridges, and the margin of the adult shell is deeply 

 crcnulated. 



