129 



round as a pea, another, S. mhidata, should be long and tuberculated ; 

 both forms, however, exhibit the peculiar elevation of the apex after the 

 manner of a rude mammillary style or column. 



Species. 



1. Astericola, Broderip. 3. pyramidalis, Reeve. 



2. coraUina {Helix), Chemn. 4. subidata, Sowerby. 



5. stylifera {PJiasianella), Tui'ton. 



Fi(/ure. 



Styliper pyramidalis. pi. 13. Fig. 56. Shell, showing the aperture 

 and transparent glassy structure. — From Mr. Cuming's collection. 



Family 7. TURBINACEA. 



Shell ; tubermdated, either conical or elongately turriculated, some- 

 times closely sometimes loosely convoluted ; aperture entire at 

 the base, with no indication of any sinus. 



We now pass to a division of the pectinibrancliiate order of Gastropods 

 distinguished by their less voracious habits, and the more tubularly convo- 

 luted structure of their shell. They are rarely provided with any proboscis 

 like the carnivorous tribes of this order, and exist chiefly, if not altogether, 

 on vegetable matter ; hence, as a general rule, their shell is less solid, 

 though rarely fragile. 



The genera of tliis family, amounting to twenty in number, correspond 

 in a manner to the Linnsean Trochus and Turbo, and the shell is mostly 

 hned with an iridescent pearly nacre. The varieties of coloured beaded 

 sculpture are most diversified in Trochus, whilst in Pfiasianella and Bmi- 

 kivia a bright array of colours is exhibited on a plane surface, without 

 the aid of sculpture. The resources of architectural ornament are perhaps 

 nowhere more beautifully represented than in Belplmmla, in one species 

 of which genus the tubercles are prolonged into a lofty diadem of vaulted 

 spines. In Scalaria a singular effect is produced by a periodical deposit 

 of the reflected margin of the aperture, leaving the whorl encircled by so 

 many rings. In Phorus the anunal exercises the remarkable property of 

 agglutinating to the surface of its shell the various debris of corals, shells, 

 or stones it may be in contact with ; and each species shows a different 

 modification of tliis habit. 



By far the larger portion of the Turhinacea are inhabitants of the Eastern 

 World. 



