MM. Wilson and Crick—The Lias Marlstone of Tilton. 303 
Turgo rucirera, Moore, 1867. Plate IX. Figs. 10a, 108, 11. 
1867. Turbo rugifera, Moore, Middle and Upper Lias, Proc. Somerset Arch. 
and Nat. Hist. Soc. vol. xiii. p. 209, pl. vi. figs. 23, 24. 
Syn. ,, Turbo coronatus, Moore, Ibid. p. 209, pl. vi. figs. 21, 22, 22*. 
Syn. ,, Pleurotomaria costulatum, Moore, Ibid. p. 208, pl. v. figs. 12, 13. 
Fresh description.—Shell turbinated, conical, umbilicated, apex 
acute; whorls 6-7, convex, narrow, with a broad flattened area 
bounding the sutures anteriorly, ornamented by sharply raised spiral 
lines, of which there are six or seven on the penultimate whorl, 
crossed by numerous fine, regular, close-set oblique radial lines, which 
raise the spirals into neat granulations at their decussations; base 
very slightly convex, umbilicus deep and generally large, with a 
squarely angulated and crenulated edge; aperture nearly round and 
nearly free from the last whorl; outer lip thin, inner lip with a 
lunate shelly expansion anteriorly. A few fine spirals may mark 
the circumference of the base, and very faint concentric striz are 
sometimes discernible between these and the centre of the base, over 
which the fine radial lines are continued in flexuous curves. Height 
9 mm.; Diameter 8 mm. to 9 mm.; Spiral angle 60° to 92°. 
Note.—There is evidently considerable variation within the limits 
of this species, and different appearances are presented by different 
individuals according as the spire is more raised or depressed, and 
according as the varying relative strength of the spirals gives a 
rounded or an angulated appearance to the whorls. It is not there- 
fore surprising that the late Charles Moore made three species out 
of the three variable specimens of Turbo rugifera which he obtained 
from the Middle Lias Marlstone of Ilminster. The specimens 
collected by Mr. Crick at East Norton serve to link these three 
forms together, and indicate that Turbo rugifera is the true type. 
Having carefully examined the type of Pleurotomaria costulatum, 
Moore, in Bath Museum, I see no reason for considering that shell 
a Pleurotomaria. It shows no trace of a sinus-band, and appears to 
be only a highly granular and somewhat squarely-keeled example 
of Turbo rugifera, Moore. Turbo coronatus also is only a more fully 
grown shell of the same type, with the difference that the greater 
prominence and coarseness of one of the spirals gives its whorls a 
coronated aspect. 
Marlstone Rock, Tilton (Hast Norton embankment). 
TROcHUS ROTULUS, Stoliczka, 1861. Plate IX. Figs. 12a, 120, 12c. 
1861. TZrochus rotulus, Stol., Gast. und Aceph. der Hierlatz-Schichten, Jahrbuch. 
der k. k. Reichsanstalt (Wien), vol. xliii. p. 178, pl. i. f. 7. 
In the Journal of the Northampton Natural History Society for 
18831 Mr. EH. A. Walford, F.G.S., quotes this fossil from the Marl- 
stone Transition-bed of Aston-le-Wall and Appletree, and gives an 
illustration (loc. cit. fig. 5), which can however hardly be con- 
sidered a satisfactory representation of this very elegant little shell. 
I trust the figures here given may be more successful. Trochus 
1 Journ. Northants Nat. Hist. Soc. vol. ii. (1883) p. 296, pl. fig. 5. 
