MALACOZOA. GASTEROPODA. PfiCTINIBRAXCHIATA. 133 



This most elegant shell appears to be Trochus Martini of 

 Mr. Smith, described and figured by Capt. Brown, in vol. viii. 

 Wernerian Transactions. The figure there given agrees in all 

 respects, excepting the lower ridges of the whorls not being 

 granulate, although described as being so. 



Trochus Martini. Smith, Wem. Trans, viii. 99. PI. 1. f. 26. 



4. Trochus cinerdriiis. Grey Purple-sirealced Pijramid-SheU. 



Shell depressedly conical, somewhat convex, lunbilicate, 

 with about five longitudinally sulcato-striate whorls, the last 

 angulate ; the sutures somewhat distinct ; the umbilicus nar- 

 row ; the mouth roundish, obliquely depressed ; the colour 

 pale grey, with radiating undulated reddish-purple lines, the 

 interior pearly. Diameter about eight-twelfths of an inch, 

 height about seven-twelfths. 



Individuals vary much in form, and considerably in colour. 

 When young, the^cone is much depressed, and scarcely convex, 

 of a grey or whitish tint, or reddish-grey, distinctly radiated 

 with purplish-red lines or bands, which are more or less vm- 

 dulated. As it enlarges, the spire becomes proportionally 

 more elevated and convex, and the markings less distinct. 

 Ultimately the height of the cone is equal to its breadth, and 

 the umbilicus becomes nearly covered. The apex is very 

 minute and thin, and being not unfrequently abraded, the 

 pillar cavity is open at both ends. Generally the lines next 

 the sutures, especially on the last whorl, are somewhat granu- 

 late. 



Abundant on stones and rocks, among fuci, especially in 

 pools left by the tide. 



Trochus umbilicatus. Mont. Test. Brit. 286. — Trochus umbili- 

 caris. Penn. Brit. Zool. iv. 126. PI. 80. f. 106. — Trochus cinerarius. 

 Mont. Test. Brit. 284. — Trochus lunbilicatus. Flem. Brit. Anim. 

 322. — Trochus cinerarius. Flem. Brit. Anim. 322. — Trochus cine- 

 rarius. Lamk. Syst. vii. 29. 



5. Trochus tumidus. Tumid Pjiramid-Shell. 



Shell convexo-conical, with the pillar perforated by a small 

 aperture ; the base rather flat ; the mouth roundish ; the in- 

 terior pearly and iridescent ; the whorls five, depressed above, 

 the last sloping and angulate, all longitudinally striate, yel- 

 lowish or brownish-white, with transverse waved lines of dusky 

 or purple. Diameter about four-twelfths, height about three- 

 twelfths. 



M 



