UNIVALVE SHELLS. 47 



\r\g, with an inserted pillar, and falling on the side when placed upon the 

 base. 



Trochus popillosus. The Pimpled Trochus. Plate VIII. 

 fig. 27. Conic, imperforate at the base, spirally granulated, and 

 not marginated at the edges of the volutions ; body tumid, and 

 spire tapering abruptly to an acute apex, flesh-coloured ; one and 

 a half inches long. 



Trochus umbilicatus. — The Umbilicated Trochus. Plate 

 III. fig. I. Shell conico-convex, flattish, rounded at the top ; 

 apex depressed, volutions five, slightly emarginate, defined by a 

 fine line ; spirally striated, rather whitish, with zigzag lines of 

 purple ; aperture compressed and angulated ; with a large um- 

 bilicus which extends to the apex. Found on the Northumber- 

 land and Yorkshire coasts. 



c Aperture, u umbilicus. 



The Trochi inhabit the ocean, with the exception of a few land species. 

 They generally frequent pools, which are wet when the tide recedes ; some 

 few of them live in very deep water. 



Genus. 28.— TURBO. 



Animal a Limax ; shell univalve, spiral^ and solid ; aperture 

 contracted, orbicular, entire. 



The shells composing this genus are divided into five families: *with the 

 pillar-margin of the aperture dilated and imperforate ; **solid and imperfo- 

 rate ; ***solid, perforated ; ****cancellated ; *****tapering. 



Turbo rudis.^THE Rustic Turbo. Plate IX. fig. 23. Sub- 

 oval, faintly striated transversely, with five tumid volutions ; 

 outer lip thick, glossy within ; dull yellow, drab, or fawn colour- 

 ed ; volutions separated by a deep suture. Three-fourths of an 

 inch long; inhabits the British coasts. 



Turbo terebra The Wimble Turbo. Plate III. fig. 9. 



(Turritella terebra, Lamarck.) Taper^ pointed, with twelve 

 or sixteen volutions, and numerous strong, spiral stria, the inter- 

 mediate spaces are prominent and acute ; white, reddish or cream 

 coloured ; one and a half inches long. Inhabits the British seas. 



This figure is polished down, to show the internal structure 

 of the columella, f. body ; M M m, columella. 



Turbo costatus. — The Ribbed Turbo. Plate III. fig. 12. 

 (Pyramis costatus, Brown.) Shell sub-pellucid, white, and 

 subturreted; volutions five, with prominent, longitudinal ribs, a 



