LIGUUS. 403 



tween the central and adjoining marginal teeth which is very marked ; in the 

 centrals the lower margin of the base of attachment is more expanded than the 

 cutting edge, the reverse of which is found in the marginals. 



The marginals retain this general form to the extreme edge of the mem- 

 brane, but they decrease greatly in size upon the edge. The outer marginals 

 have to their cusps a small side spur, gouge-shaped as the cusp itself ; the ex- 

 treme marginals have such a spur at either side. In both cases the cutting 

 edge springs from the outer side of this side spur, which must be considered as 

 representing the side cusps of the usual Helicea type of dentition. I have 

 elsewhere (Ann. Lye. N. H. of N. Y., XI. 39) shown that this type of tooth is 

 but a modification of the usual type brought about by the expansion, bluntly 

 rounding and shortening of the cusps, and the still greater expansion, bluntly 

 rounding and shortening of the cutting points, which are quite changed into 

 wide cutting edges. 



I have given on PI. X. Fig. G, a group of central and marginal teeth in a, 

 an outer marginal in c, a marginal in profile in d. 



The allied species L. virgineus differs from fascialus in having a long blunt 

 cutting point to its central tooth, and by.the presence of several true lateral 

 teeth with long cutting points, also in the presence of several teeth showing a 

 gradual change from the laterals to the marginals. A full description and de- 

 tailed figures of its dentition are given by me in Ann. Lye. Nat. Hist. N. Y., 

 XI. 41, PI. III. 



Liguus is nearly allied in its lingual dentition to Orthalicus, but in that genus 

 also I have found one species with true lateral teeth, as will be shown below. 



Liguus fasciatus, Muller. 

 Vol. III. Pis. LV., LVL, LVII. 



Shell imperforate, conical, rather thick, smooth, shining, minutely striated ; 

 whorls 7 to 8, convex, decreasing in diameter gradually and regularly from the 

 body- whorl to the apex ; suture impressed ; apex obtuse, commonly white, 

 sometimes rosy ; aperture suboval, purely white internally, sometimes with a 

 thickened ridge within, and parallel to the peristome ; peristome acute, some- 

 times crenate ; columellar margin with a thin callus, sometimes rosy ; columella 

 subtruncate in the young, entire in the mature shell, imperforate; surface 

 beautifully variegated with broad, entire or interrupted bands, lines, and spots 

 of brown, with bands and lines of green and yellow, and with lines of rufous, 

 revolving upon the whorls from the apex to the aperture, but more distinct 

 upon the outer whorls ; a single system of coloring prevails in some shells, 

 while in others there is a mingling of all of them upon the same specimen. 

 Extreme length, 53 mill. ; diameter, 23 mill. 



Buccinum fasciatum, Muller, Verm., II. 145 (1774). 



Bulla fusciata, Chemnitz, Conch., IX. Tab. CVII. Figs. 1004-1006. 



