126 MOLLUSCA FROM THE CRAG. 



Catalogue was 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 speci- 

 mens, are nearly equidistant, and the shell is smooth between them, with the excep- 

 tion of lines of growth ; the lower ridge at the angle of the volution appears to be 

 double. On those from the Coralline Crag, 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 cancel- 

 lated 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 

 he main land of Zetland. 



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



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



— granulatus. Born. Test. Mus. Vind. t. 12, fig. 9-10, 1780. 



— papillosus. Don. Brit. Shells, 4, t. 127. 



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



— similis (?). J. Sow. Min. Conch, t. 181, fig. 2, 1817. 



— granosus. S. Wood. Catalogue 1842. 



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



— Dekinii (?). pi. 36, fig. 10. 



Tr. Testa orbicidato-conicd, obliqud, imperforatd, basi dilatatd ; apice peracuto ; 

 anfractibus convexiusculis ; striis transversis, alternatim majoribus et granulosis injimd facie 

 plamdatd, concentrice striata et granulatd ; aperturd dilatatd, tetragond. 



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

 slightly convex, covered with transverse, granulate strise ; 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 strise on the upper surface alternate one large and one small. 



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

 Trochus subexcavatus. S. Wood. Catalogue 1842. 



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

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

 striata el granulatd ; aperturd tetragond. 



