CONCHOLOGY. 133 



right edge having a thickened varix. Inhabits the Mediterranean 

 and Northern Seas. Two species. 



Struthiolaria nodulosa. Struthiolaria crenulata. 



9. Genus Ranella. PL XL 

 ^^tiiinal. Unknov/n. 



Shell. Oval, and, as it were, depressed by the preservation of 

 each side of a longitudinal thickened band ; aperture oval, almost 

 symmetrical by the excavation of the columellar edge, terminating 

 anteriorly by a short canal, often a little sloping; a sinus at the 

 posterior junction of the two edges. This genus forms a distinct 

 division between the Murex and Struthiolaria. Inhabits the 

 Northern and Mediterranean Seas. One species is found in 

 America. Ffteen Uving species. Five fossil. 



Ranella gigantea. Ranella leucostoma. 



R. candisata. R. Argus. 



R. ranina. R. spinosa. 



R. bufonia. R. granulata. 



R. granifera. R. semigranosa. 



R. bitubercularis. R. crumena. 



R. anceps. R. pygniEea. 



R. caudata*. 



10. Genus Murex. PI. XI. 



Animal. See Pleurotoma, above. 



Shell. Usually oval ; the spire but slightly elevated, roughened 

 with longitudinal, transversal bands or varices ; aperture small, 

 quite oval, and synnnetrical by the excavation of the left edge, 

 formed by a lamina applied upon the columella, terminated an- 

 teriorly by a middling canal sometimes very long and closed ; the 

 right edge more or less furnished with varices. Operculum horny, 

 complete, oval, nearly circular, with sub-concentric partitions; 

 summit terminal. This genus comprehends only such shells as 

 have only three or more varices on each whorl. These varices 

 show how often the animal has increased the size of its shell. 

 Found in all seas. Seventy-three living species. Two fossil. 

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