Trochus. 



MOLLUSCA. 



77 



21. T. BISERTUS — The Two-plaited Trochus, pi. XXXIX. 

 fig. 28. 



Trochus bisertus. Phillips, Geo. of Yorkshire, I. p. 129, pi- 

 ll, fig. 27. 



Shell conical ; sides nearly flat ; base prominent ; each volu- 

 tion provided with two plaits of small, nearly equidistant 

 papilla; ; the intervening spaces covered by minute longitudinal 

 strias. 



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, pi. 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 Inferior 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, 

 pl.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 striae, the 

 upper ones upon each volution most prominent, and crossed by 

 longitudinal, oblique, undulating hues, 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 striae ; 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 striae, 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 striae, which are in several parts very 

 obscure, and are semicircular where they cross the tubercular 

 band ; base convex, furnished with strong tubercular concentric 

 striae, umbiHcated, 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 Segwick'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 carinated edge, and elevated 

 rather indistinct striae ; base rather convex, with concentric 

 striae, which are strongest towards its centre ; aperture rhom- 

 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 strisB ; 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 



