Thociius. MOLLUSC A. TROCHUSIDvE. 325 



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

 Inferior Oolite. 



15. T. pallium Conical, depressed, with concentric furrows, and diverging 



strife ; 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. f. 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 r-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. reticularis Conical, transversely reticulato-striated ; whorls bicari- 

 nated ; base convex Sower. Min. 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 ; pillar-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 granules ; aperture quadrangular ; pillar-cavity, along one 

 edge of the aperture, truncated. (T. nodulosus, Brander, Toss. Hant. f. 6.) 

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



23. T. linearis.—" Conical, wreaths slightly convex, transversely striated, 

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

 umbilicus obscured by the last volution ; aperture transversely depressed." — 

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

 other species, from the same formation, are given byMrMantell, ib. t. xviii. 

 f. 7- f- 9- and 16. 



Gen. SOLARIUM. — Pillar cavity spreading, and crenulated 

 at the margin of the whorls. 



1. S.patvlum 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.-=-T)iscoh\, outer edge sharply carinated ; edge of the pillar- 

 cavity rounded, transversely wrinkled ; 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. 



