Modification of the Apex in Gastropod Mollushs. 699 



Family TRITONIID^. 

 Genus GYRINEUM Link. 1807. 

 Banella Lamarck. 1812. 

 G-yrineum al1)0'raricosa Eeeve. (Fig. 48.) 



Apex small, rounded, smooth, shining, consisting of two and 

 a-half regularly increasing whorls. The post-nuclear whorls are 

 very nodulous and are shouldered. In some specimens the nuclear 

 whorls appear a trifle malleated. The color is white or horn. 



There seems to be a a great amount of uniformity among the 

 nuclear whorls of this genus. The following species all have 

 apices of the same type as albovaricosa, varying only a trifle in 

 relative heights and widths. The number of whorls is the same 

 in all ; a number of specimens of each species have been ex- 

 amined. 



Gyrineum elegans Beck. 

 Gyrineuiu lampas Lamarck. 

 Gyrineum sulbgranosum. Beck. 

 Gyrineum spinosum Lamarck. 

 Gyrineum lividum Eeeve. 

 Gyrineum affine Broderip. 

 Gyrineum pulclirum Gray. 



Genus TRITONIUM Link. 1807. 



IHton Montfort. 1810. 



Of a collection of some twelve species of this genus, comprising 



about a hundred specimens, not a perfect apex could be found. 



From an examination of a broken nucleus, I should say the apex 



was similar to that of Gyrineum. 



Family CASSIDID^. 



Genus CASSIS Lamarck. 

 Cassis granulosa Lamarck. (Fig. 49.) 



Apex small, rounded, smooth, shining, white, consisting of two 

 and a-half whorls. The first whorl is very small and narrow, and 

 its apex seems to be buried in the coil of the second whorl. The 

 last two whorls are broad and rounded. The post-nuclear whorls 

 are nodulous. The whole apex has the appearance of a mamma 

 very much flattened at the top. 



