36 IANTHINA. 



Genus IANTHINA, Lam., 1799. 

 I. FRAGILIS, Lam. PI. 9, figs. 94-5 ; PI. 10, figs. 6-10. 



Whorls slopingly convex, with obtusely angulated periphery, 



outer lip of aperture very slightly sinuous, violaceous white 



above, uniform purplish or violaceous below. Diam. T5 inches. 



Mediterranean, Atlantic 0., Indian 0., Pacific 0. 



This is probably Linnaeus' Helix lanthina. 



Reeve and others distinguish two species which they suppose 

 Lamarck at first confounded under the name of I. fragilis; they 

 restrict this name to the more acutely angulated forms (figs. 94, 

 3, etc.), whilst /. communis, Lam. (fig. 99) the name by which 

 he intended to replace his I. fragilis is reserved for those with 

 obtuse periphery. I confess that I cannot divide them satisfac- 

 torily ; consequently I include here as synonyms a series of 

 intermediates, which have received the names of: 



/. Costae, Morch, proposed for /. bicolor, Costa (not Menke) ; 

 /. vulgar is, Gray ; Helix lanthina, Forskal ; /. violacea, Adams ; 

 /. penicephala, Peron ; /. violacea, Morch ; /. grandis, Brown ; 

 /. striulata, Carp. = I. Carpenteri, Morch (fig. 3), and var. con- 

 torta, Carp., from Mazatlan ; /. Orbignyi, Morch ; I. bicolor, 

 Menke. 



Yar. PLANOSPIRATA, Ads. and Reeve. Figs. 94-98. 



Depressed, with slopingly convex whorls, obliquely plicately 

 striated ; columella arched, somewhat dihitely reflected ; aper- 

 ture transverse, a little sinuous on the middle of the outer lip. 



Diam. 1*4 inch. 



Atlantic Ocean, St. Helena, etc. 



May be nominally distinguished from I. fragilis by its more 

 rounded periphery and more depressed spire, as well as by the 

 light color of the base immediately around the columella; but 

 apparently connects with it by intermediate stages. Among 

 these, having the form of planospirata, but with usually uniform 

 purple base, may be placed here as synonyms I. depressa, 

 Reeve (fig. 97); /. cserulata, Reeve (fig. 9fi) ; /. casta, Reeve 

 (fig. 95) ; I. balteata, Reeve (fig. 98) ; forms with more elevated 

 spire, approaching /. fragilis are /. bicolor and /. fragilis, of 

 Lesson. 



