Trochus. 
MOLLUSCA. 
77 
21. T. bisertus. —The Two-plaited Trochus, pi. XXXIX. 
fig. 28. 
Trochus bisertus . Phillips, Geo. of Yorkshire, I. p. 129, pi* 
11, fig. 27. 
Shell conical; sides nearly flat; base prominent; each volu¬ 
tion provided with two plaits of small, nearly equidistant 
papillae; the intervening spaces covered by minute longitudinal 
striae. 
Found in the Blue Wick in the Inferior Oolite Sand at Cold 
Moor, Yorkshire, by Mr. Williamson. 
22. T. pyramidatus. — The Pyramidal Trochus, pi. 
XXXIX. fig. 29. 
Trochus pyramidatus. Phillips, Geo. of Yorkshire, I. p. 
129, ph 11, fig. 22. 
Shell conical, abruptly tapering to an acute apex; spire con¬ 
sisting of four slightly raised volutions, well defined by the 
sutural line, and provided with oblique, longitudinal flattened 
ribs; base flat; aperture subquadrangular. 
Found in the Blue Wick of the Iuferior Oolite Sand at 
Cold Moor, near Glaizedale, Yorkshire, by Mr. Bean of Scar¬ 
borough. 
23. T. tornatilus. —The Turned Trochus, pi. XXXIX. 
fig. 30. 
Trochus tornatilus . Phillips, Geo. of Yorkshire, I. p. 102, 
pi. 4, fig. 16. 
Shell much depressed; spire consisting of three volutions, 
but little elevated above the body volution, which is rounded 
on the sides; a narrow flattened space emanates from the inser¬ 
tion of the outer lip, and winds spirally along the superior 
margin of the volutions. 
Found in the Coralline Oolite at Scarborough. 
24. T. punctatus _The Punctured Trochus, pi. XXXIX. 
fig. 31. 
Trochus punctatus* Sowerby, Min. Conch. II. p. 211, pi. 
193, fig. 1 and 4. Fleming, Brit. An. p. 324. 
Conical, its height exceeding the diameter of the base, sides 
nearly flat; volutions with numerous, minute, spiral stria?, the 
upper ones upon each volution most prominent, and crossed by 
longitudinal, oblique, undulating lines, the lower ones studded 
with minute granulations; between every two sets, a narrow 
spiral fillet. 
Found in the Inferior Oolite at Dundry, in the neighbour¬ 
hood of Bristol. 
25. T. imbricatus _The Imbricated Trochus, pi. 
XXXIX. fig. 35. 
Trochus imbricatus . Sowerby, Min. Conch. III. p. 127, pi. 
272, fig. 3, 4. Fleming, Brit. An. p. 325. 
Pyramidal, subturreted, its height being nearly double its 
breadth at the base; volutions angular, obliquely flattened 
above, imbricating each other at their base; each volution 
provided with several elevated, thread-like lines, crossed by 
numerous fine longitudinal stria?; base very convex; striated 
in the same manner as the superior portion of the shell; fur¬ 
nished with a closed umbilicus. 
Found in the Lias Clay, near Cheltenham. 
26. T. elongatus. —The Elongated Trochus, pi. XXXIX. 
fig. 33. 
Trochus elongatus. Sowerby, Min. Conch. II. p. 211, pi. 
193, fig. 2, 3. Fleming, Brit. An. p. 324. 
Conical, greatly elongated, its breadth at the base being only 
two-thirds its height; with nine or ten concave-sided volutions, 
each with a rounded, broad prominent band at the base, with 
an obscure fillet a little below the middle; whole surface with 
strong spiral stria?, granulated near the apex; and each of the 
volutions slightly undulated near its superior edge. 
Distinguished from T. punctatus by being more elongated, and 
the margins of the volutions being more produced. 
Found in the Inferior Oolite at Dundry, near Bristol. 
27. T. pallium. —The Mantled Trochus, pi. XXXIX. fig. 
34. 
Trochus pallium . Fleming, Brit. An. p. 325. Trochus 
ornatus, Sowerby, Min. Conch. III. p. 39, pi. 221, fig. 1. 
Shell subconic, depressed; body large; spire small, consisting 
of three or four volutions, depressed above in the middle, each 
provided with a band of elongated divergent tubercles on its 
upper margin; body with three series of tubercles; the whole 
shell with divergent stria?, which arc in several parts very 
obscure, and are semicircular where they cross the tubercular 
band; base convex, furnished with strong tubercular concentric 
striae, umbilicated, and plaited in some instances; margin with 
large crenulations. Height about half its diameter. 
Found in the Inferior Oolite at Dundry, near Bristol. 
28. T. Segwickii —S eg wick’s Trochus, pi. XXXIX. fig. 
32. 
Trochus Segwickii. Fleming, Brit. An. p. 325. Trochus 
concavus , Sowerby, Min. Conch. III. p. 127, pi. 272, fig. 1. 
Conical, smooth; volutions somewhat concave above, and 
convex below, with an obtuse carinafed edge, and elevated 
rather indistinct striae; base rather convex, with concentric 
striae, which are strongest towards its centre; aperture rliom- 
boidal; umbilicus closed. 
Found in the Suffolk Crag. 
29. T. abbreviatus. — The Shortened Trochus, pi. 
XXXIX. fig. 36. 
Trochus abbreviatus. Sowerby, Min. Conch. II. p. 212, pi. 
193, fig. 5. Fleming, Brit. An. p. 324. 
Shell conical, abbreviated; the base of each of the volutions 
provided with a greatly produced, rounded spiral fillet; whole 
surface with fine spiral stria?, which are faintly decussated by 
oblique lines of growth, these are semicircular as they pass 
over the fillet; base rather flat, and furnished with sharp con¬ 
centric stria?; the breadth at the base exceeds its height. 
Found at Dundry in the Inferior Oolite. 
Genus XXXIV_SOLARIUM — Lamarck. 
Shell subdiscoidal beneath; spire obtusely conical; in 
some instances of a more lengthened conical form; the 
lower margin of the body angular, and rather sharp; 
umbilicus broad and deep, and reaching to the apex, its 
margin crenulated, and exhibiting the internal edges of 
the superior volutions in the form of a winding gallery; 
aperture wide, trapeziform, with its angles somewhat 
rounded, and the peritreme or outer lip thin and sharp; 
outside covered with a horny epidermis; operculum 
u 
