260 APPENDIX. 



Vol. ii. p. 549. Ianthina communis. 



Plate CXXXIII. f. I. 



Until the genus Ianthina shall have experienced a thorough 

 revision, and the effect of local circumstances in producing varia- 

 tion of colouring, chasing, and contour upon its migratory mem- 

 bers shall have been duly estimated, it will be hazardous to define 

 the limits of the several varieties or species which by the past 

 generation of conchologists were included in the Helix Ianthina, 

 by the present in the i". fragilis or communis. Krauss, in his 

 useful work on the testacea of S. Africa, remarks that the indi- 

 genous shell figured by Chemnitz (Conch. Cab. vol. v. pi. 166, 

 f. 1577, 1578) is very distinct from the Neapolitan one termed 

 bicolor by Philippi, though both are usually cited as identical. 

 Our British examples again, seem different from either, and were 

 considered so by Dr. Leach, who, we are informed by Mr. Jeffreys, 

 termed them Britannica* 



The pale basal zone, however (it seems always present in the 

 younger specimens), is assuredly of not more than varietal im- 

 portance ; Mr. Cuming possesses fine adult examples, taken alive 

 by himself at Peranzabuloe, in Cornwall, in which the band is 

 sometimes conspicuous, sometimes partially apparent, sometimes 

 entirely obsolete. 



As the shell delineated in Plate LXXIX was immature, we have 

 likewise given a representation of a fully grown specimen in Plate 

 CXXXIII. The latter, which is taken from an Irish example, 

 much resembles the engraving in Brown's " Illustrations," and 

 differs from those previously described in so many particulars 

 that it becomes of importance to specify them. 



The shape is not horizontally compressed as in the bicolor of 

 Philippi, but is almost biconoidal ; the spire, which is about 

 ecpial in height to the aperture, being elevated, and the lower disk 

 comparatively produced, so that the length is very nearly equal 



* Our foreign synonymy was drawn up in the belief, that the British examples 

 were specifically the same as those of the Mediterranean. Should this supposi- 

 tion prove erroneous, most of our references (the figures of the two Sowerbys, of 

 Reeve, Blainville, the Penny Cyclopaedia, and probably Crouch) must be ex- 

 punged and transferred to the latter. 



