186 MAZATLAN UNIVALVES 



bus primis lirulis concentricis acutis pulcherrime instructis, 

 postea lineas incrementi monstra Mbus ; lineis spiralibus plus 

 minusve distinctis ; angulo mediano distineto ; superne pallidis- 

 simd, inferne violascente ; columelld tenuissimd, plica 'acutd 

 instruct d, ad basim plus minusve extort d ; labro plus minusve 

 sinuato, sinu angulato ; labio vix projiciente, tenuissimo. 



Comp. lanthina fragilis, D'Orb., B. M. Cat. Cuba Moll. p. 23, 

 no. 258 : B. M. Cat. D'Orb. Moll. p. 36, no* 316 : B. M. 

 Cat. Can. Moll. p. 15, no. 107 : ( = 1. communis, Lam. An. s. 

 Vert. vol. ix. p. 4, pars.) 



This shell may hereafter prove to be identical with one of 

 the various Atlantic species. There are two forms called 

 I. fragilis from the W. Indies ; one agreeing with this in the 

 separation of colours and sharp columella, but with more pink 

 in the violet tinge ; the other agreeing in tint, but with the 

 colour diffused and the columella coarser. All differ essentially 

 from the British I. communis, (of which there are two very 

 different ? varieties) in the very fine concentric liration of the 

 upper whirls, and in the character of the nucleus. This, in 

 I. communis, is sunken, but not flattened at the apex ; in the 

 tropical species it is rather prominent, but flattened at the top. 

 It is not so horny as in the next species, and is always persis- 

 tent. The shape is tolerably constant ; but the amount of 

 sinuation in the outer lip somewhat varies. The very young 

 snell is globular, without angular keel. Long. '78, long. spir. '44, 

 lat. I', di 



jffab. Mazatlan ; abundant ; L'pool Col. 



Tablet 868 contains a very young sp. '04 across, broken, but 

 shewing the transition between the oblique and straight por- 

 tions-. r869, a young sp. with fry adhering to the suture. 870, 

 3 sp. depressed form. 871, 5 sp. normal state, jun. 872, 5 do. 

 adult. 873, 4 sp. spire elevated. 874, 3 sp. basal angle pro- 

 duced. 875, 4 do. shoulder curiously swollen. 876, 7 do. 

 broken and mended by the animal. 



242, b. IANTHINA STEIULATA, var. CONTOBTA. 



I. ?striulata, columelld maxime contortd, ad basim productd, 

 reflexd, sinu may no, haud angulato. 



This shell when taken alone would certainly be regarded as 

 a distinct species : but as several specimens of I. striulata shew 



