124 MOLLUSCA FROM THE CRAG. 



doubt respecting the locality, and unfortunately there is nothing within the shell that 

 will assist in the determination, though I am strongly inclined to believe it belongs to 

 the Coralline Crag period, and that the shell was found at Gedgrave. 



The lower part of the volution, near the outer angle, is furnished with a double 

 row of tubercles, above which are two spiral threads, also tuberculated ; the whole is 

 crossed with distinct, oblique, subimbricated lines of growth, and upon the base are 

 four or five circular or rather spiral ridges, also crossed by prominent lines of growth. 

 It has a prominent tooth or projection at the lower part of the columella. The shell 

 is beautifully nacreous beneath the outer coating. 



2. Trochus ziziphinus. Linn. Tab. XIII, fig. 9, a — h. 



Trochus ziziphinus. Linn. Syst. Nat. p. 1231. 



_ _ Mont. Test. Brit. p. 274, 1803. 



_ _ Brown. Illust. Brit. Conch, pi. 45, fig. 16-22. 



— L^viGATUs. J. Sow. Min. Conch, t. 181, fig. 1, 1817. 



— coNCAVUs. - - - t. 272, fig. 1, 1823. 



— Sedgwickii. J. Sow. Syst. Catalogue 1835. 



— — Nyst. Coq. foss. de Belg. p. 380, pi. 35, fig. 20, 1844. 



— L.^viGATUs. ... p. 379, pi. 36, fig. 11. 



— CONULUS, var. j3. Phil. En. Moll. Sic. vol. i, p. 175, 1836. 



— coxuLOiDES. Lam. 2d edit. torn. Ls, p. 142, 1843. 



— ZIZIPHINUS. iS. Wood. Catalogue 1842. 



— PSEUDO-ZIZIPHINUS. Id. 



Tr. Testa orbiculato-conicd, obliqud ,- apice acuta, granulato ; anfradibus planis aut 

 concavis ; transversim et tenuiter striatis ; ad margmem mbcarinatis ; injimd facie convexd ; 

 columelld obliqud ; aperturd dilatatd, tetragond. 



Shell orbiculato-conical, oblique, fragile, with an acute apex and granulated spire ; 

 sides flat or slightly concave, covered with fine, or occasionally with coarse striae; base 

 of volution submarginate, and slightly extended, somewhat convex beneath, and 

 concentrically striated; aperture trapezoidal. 



Axis, \\ inch; diameter, variable. 



Locality. Cor. Crag, Sutton and Ramsholt. 



Red Crag, Sutton. Recent, Britain. 



This handsome shell is not rare, but it is difficult to obtain it in perfect condition, from 

 its extreme fragility. Nearly all my specimens are from the Coralline Crag ; they arc 

 covered with fine striae, and differ from the common form of the recent T. ziziphinus, which 

 are more or less ridged. Prof. E. Forbes informs me he has dredged up specimens in 

 the Scottish seas with the same kind of fine striae, and as that is the only essential 

 diS"erence between our shell and T. ziziphinus, they are presumed to be identical. 

 The first three or four volutions are covered with about five granular ridges, but in 

 many specimens the upper ridge is the only one on which these granulations are 

 preserved. The variety with concave sides has naturally a corresponding convexity 

 of base, and the edge of the volution slightly extended, giving it a greater diameter. 



