126 MOLLUSCA FROM THE CRAG. 



without description, although of prior date, it must of course give place to the one he has 

 employed. The ridges, which are but four upon my specimens, are nearly equidistant, 

 and the shell is smooth between them, with the exception of lines of growth ; the 

 lower rido-e at the angle of the volution appears to be double. On those from the 

 Coralline Craf, the upper ridge only is crenulated on the last whorl, the shell having 

 lost a portion of its outer covering. In one from the Red Crag, the upper three ridges 

 are distinctly nodulous, while the lower one alone is smooth. In the young state three 

 volutions are crenulated upon all four ridges, which appear to vanish as the shell 

 grows older, and it is beautifully cancellated on the obtuse apex. The recent analogue 

 appears to have been obtained, living at the depth of fifty fathoms, by Mr. M' Andrew, 

 about forty miles west of the main land of Zetland. 



5. Trochus papillosus (?). Ba Costa. Tab. XIII, fig. 6, a — c. 



Trochus papillosus. Ba Costa. Hist. Nat. Test. Brit. p. 38, pi. 3, fig. 5-6, 1778. 



— GKANULATUS. Bom. Test. Mus. Vind. t. 12, fig. 9-10, 1780. 



— PAPILLOSUS. Bon. Brit. Shells, 4, t. 127. 



— TENUIS. Mont. Test. Brit. p. 275, pi. 10, fig. 3, 1803. 



— siMiLis (?). /. Soio. Min. Couch, t. 181, fig. 2, 1817. 



— GKANOSUs. iS. Wood. Catalogue 1842. 



_ _ Nyst. Coq. foss. de Belg. p. 377, pi. 35, fig. 19, 1844. 



— Dekinii (?). .... pi. 36, fig. 10. 



Tr. Testa orbiculato-conicd, obliqiid, imjKrforatd, basi dilatatd ; apice peracuto ; 

 anfradibus convexiscidis ; striis transversis, alternatim majoribiis et (jramdosis ; infmd facie 

 planulatd, concentrice striatd et granulatd ; aperturd dilatatd, tetrac^ond. 



Shell orbiculato-conical, rather depressed, with a sharp and acute apex ; volutions 

 slightly convex, covered with transverse, granulate striae ; base somewhat flattened, 

 imperforate, and concentrically striated ; aperture expanded and trapezoidal. 



Axis, f of an inch. 



Locality. Red Crag, Sutton, Newbourn, Bawdsey, Walton. Recent, Britain. 



Small specimens of this shell are abundant in several localities, particularly at Walton- 

 on-the-Naze. From close examination of many specimens, I am induced to believe this 

 to be only a variety of the British species T. papillosus, although the base is flatter, and 

 the volutions a little more convex than in the generality of full-grown specimens of the 

 recent shell. I imagine Trochus similis of Sow. to be a variety of this species, with 

 flatter sides (fig. 6 c). The middle part of the base is generally free from concentric 

 striae, but in some specimens it is entirely covered, and the striae on the upper surface 

 alternate one large and one small. 



6. Trochus subexcavatus. S. Wood. Tab. XIII, fig. 8, a — c. 



Teochus subexcavatus. S. Wood. Catalogue 1842. 



Tr. Testa conicd, elevatd, granulatd, imperforatd ; anfractibus septem, supeme concavis 

 subexcavatis, inferne convexis ; striis transversis granulatis ; basi planulatd, concentrice 

 striatd et granulatd ; aperturd tetragond. 



