186 MAZATLAN UNIVALVES 



hus primis lirulis concentrids acuiis pulcherrime instrudis, 

 postea lineas incrementi monstrardibus ; Uneis spiralibus plus 

 minusve distinctis ; angulo mediano distinct o ; superne pallidis- 

 simd, itiferne violascente ; columella temiissima, plica acuta 

 instructa, ad hasim plus mimisve extorta ; lahro plus minusve 

 sinuato, sinu angulaio ; labio vix projiciente, tenuissimo. 



Comp. lanthina frasilis, 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.) 



Ttis shell may hereafter prove to be identical -witli 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 coloui-s 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. AH 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. Tliis, 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 

 BheU is globular, without angular keel. Long. "78, loiig. spir. •44, 

 lat. V, div. 100". 



Hab. — Mazatlan ; abundant ; L'pool Col. 



Tablet 868 contains a very young sp. •01 across, broken, but 

 shewing the transition between the oblique and straight por- 

 tions.— 869, 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 cui-iously swollen.— 876, 7 do. 

 broken and mended by the animal. 



242, h. Ianthina steiulata, var. contobta. 



J. ?.itriulata, columelld maxime contortd, ad basim productA, 

 reflexd, sinu- magno, Jiattd angulaio. 



This shell when taken alone would certainly be regarded as 

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



