Modification of the Apex in Gastropod Mollusks. 691 



hyaline in texture and color. The whole apex is very simple ; in 

 fact, the simplest kind of an apex. 



There appears, if one may judge by the material at hand, to be 

 no variation among the nuclear whorls of this genus. The follow- 

 ing species have been examined and the apex does not differ, save 

 at times in size, in the slightest degree : 



Marginella bivaricosa Lamarck, M. guttata Dillwj^n, M. nivosa 

 Hinds, M. curta Sowerby (apex darker in color than usual), M. 

 conoidalis Kiener, and M. apicina Menke (apex pinkish). 



Family YOLUTID^. 

 Genus VOLUTA Linne. 



Toluta mnsica Liniie. (Fig. 18.) 



Apex very large, rounded, smooth, consisting of four and a-half 

 whorls, regularly increasing in size. The last nuclear whorl is 

 partly buried in that of the first post-nuclear. The apex is 

 smooth, of a rusty-brown color, and is very broad ; the post-nu- 

 clear whorls are all armed with good-sized nodules. The whole 

 apex is so large that it may be easily studied with the unaided eye. 

 Five specimens have been examined, and the only variation seems 

 to be in the comparative height of the apex, some specimens hav- 

 ing the whorls flatter than in the specimen figured. 



Toluta scapba Gmelin. (Fig. 19, 20.) 



Apex verj' large, rounded, smooth, shining, consisting of three 

 and a-half whorls, which start out small and rapidly enlarge in 

 size. The extreme apex (one and a-half whorls) is very flat and the 

 whorls cannot be seen in a lateral view (see Fig. 20) ; the last two 

 whorls are broadly rounded. The color is dark (or light) brown 

 and the zigzag lines of color so characteristic of this species 

 do not appear until the first post-nuclear whorl is reached. The 

 nuclear whorls may measure 10 mill, in height and 15 mill, in 

 width. This is one of the largest apices in marine gastropods. 

 A number of perfect examples have been examined and the only 

 variation seems to be in the comparative height and breadth of 

 the apex, 



Toluta vespertilio Linn6. (Fig. 21, 22.) 



Apex small (for the genus) rounded, nodular, shining consist- 

 ing of three whorls, rapidly enlarging. The first one and a-half 

 whorls are flat as in scapha, and the following whorls are large 



