Trochus. MOLLUSCA. TROCHUSIDiE. 325 



sulcus around the middle ; base flattish. — Sower. Min. Conch, t. ccxx. f. 3 



Inferior Oolite. 



15. T. pa//JMm.— Conical, depressed, with concentric furrows, and diverging 

 strije ; whorls above depressed, with many tubercular undulations ; in the 

 middle flattened, with a longitudinal band ; base convex, umbilicated ; mar- 

 gin largely crenulated. — Sower. Min. Conch, t. ccxxi. £ 1 Inferior Oolite. 



16. T. tiara. — Depressed, conical, with diverging striae; volutions obscure- 

 ly bicarinated, deeply undulated above, concentrically striated beneath ; base 



convex, with a large pillar-cavity — Sower. Min. Conch, t. ccxxi. f. 2 Green 



Sand. 



17- T. Sedgwicki — Conical, smooth ; base carinated ; whorls concave above, 

 convex below ; margin and base striated — Sower. Min. Conch, t, cclxxii. f. 1. 

 — Suffolk Crag. 



18. T. imbricatus — Pyramidal, with several transverse threads upon each 

 whorl, crossed by fine longitudinal striae ; whorls angular, imbricating, flat 

 above, very convex beneath ; pillar-cavity closed. — Sower. Min. Conch, t. 

 cclxxii. f. 3, 4. — In Lias Clay. 



19. T. reticiilatus. — Conical, transversely reticulato-striated ; whorls bicari- 

 nated ; base convex. — Soioer. IMin. Conch, t. cclxxii. f. 2 Upper Oolite. 



20. T. Gibsii. — Conical, short, umbilicated ; sides straight ; edge obtusely 

 carinated ; base convex, reticulato-striated ; in the centre of the upper part 

 of the whorls, is an elevated band, crossed by curved striae ; aperture rhom- 

 boidal — Sower. Min. Conch, t. cclxxviii. f. 1 Chalk Marl. 



21. T. extensus — Depressed, conical ; above rugged, obliquely striated ; 

 beneath convex, smooth ; base expanded, with a broad undulated thin mar- 

 gin ; aperture oblong ; piUar-cavity not plicated, closed when old Sower. 



Min. Conch, t. cclxxviii. f. 2, 3 — London Clay. 



22. T. monilifer. — Conical, transversely striated ; volutions rather convex, 

 with three rows of tubercles, and crenated edges ; base slightly convex, bear- 

 ing six rows of gianules ; aperture quadrangular ; pillar-cavity, along one 

 edge of the aperture, truncated. (T. nodulosus, Brander, Foss. Hant. f. G.) 

 — Sower. Min. Conch, t. ccclxvii. — London Clay. 



23. T. linearis. — " Conical, wi'eaths slightly convex, transversely striated, 

 with a prominent line along the centre and base of each volution ; base flat ; 



umbilicus obscured by the last volution ; apertui'e transversely depressed." 



Mantell, Geol. Suss. 1 10. t. xviii. f. 17. Ingrey chalk-marl. Indications of three 

 other species, from the same formation, are given by Mr Mantell, ib. t. xviii. 

 f. 7- f- !)• and 16. 



Gen. solarium. — Pillar cavity spreading, and crenulated 

 at the margin of the whorls. 



1. S.;)a<M/M»n.— Depressed, whorls smoothish; margin keeled and crenulated; 

 margin of the cavity strongly denticulated. Sower. Min. Conch, t. xi. ; lower 

 right hand figures — In London Clay. 



2. S. discoideum. — Discoid, outer edge sharply carinated ; edge of the pilkr- 

 cavity rounded, transversely wrmkled ; aperture obliquely elliptical, pointed 



at each end. Sower. Min. Conch, t. xi. ; upper right hand figures London 



Clay. 



3. S. conoideum. — Conical, smooth ; aperture quadrangular ; pillar-cavity 

 deep, narrow — Sower. Min. Conch, t. xi. ; three middle figures.— Upper Oolite. 



