186 MAZATLAN UNIVALVES 
bus primis lirulis concentricis acutis pulcherrime instructis, 
postea lineas incrementi monstrantibus ; lineis spiralibus plus 
minusve distinctis ; angulo mediano distincto ; superne pallidis- 
simd, taferne violascente ; columella tenuissima, plicd acuta 
enstructd, ad basim plus minusve extortd ; labro plus minusve 
sinuato, sinu angulato ; labio vix projiciente, tenuissimo. 
Comp. Ianthina fragilis, D’Orb., B. M. Cat. Cuba Moll. p. 23, 
no. 258 :—B. A. Cat. D’ Orb. Moll. p. 36, no. 316:—B. M. 
Cat. Can. Moll. p. 15, no. 107 :—(=I1. 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 
shell is globular, without angular keel. Long.°78, long. spir. *4A, 
tat. 1°, div. 100°. 
Hab.—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.—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 clevated.—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 STRIULATA, var. CONTORTA. 
I. ?striulata, columelia maxime contorta, ad basim producta, 
reflexd, sinu magno, haud angulato. 
This shell when taken alone would certainly be regarded as 
a distinct species: but as several specimens of I. striulata shew 
