Y04 Modification of the Apex in Gastropod Mollusks. 



Genus GIBBULA Risso. 

 Gi1)1)iila forinani Payr. 



The apex of this species is in all respects like that of Callios- 

 toma langieri. Three specimens examined. 



Genus EUCHEL,US Philippi. 

 Euchelus denigratus Chemnitz. 



Apex similar in form to Galliostoma langieri^ but more rapidly- 

 enlarging, smooth and brownish red in color. A single specimen 

 examined. 



Genus CI.A]VCIJL,US Montfort. 



Clanculus periiiceus Philippi. (Fig. 58. ) 



Apex smooth, pink or red, rounded, consisting of one and a- 

 half whorls regularly increasing. The first part of the first whorl 

 is buried in the coil of the succeeding whorl. The post-nuclear 

 whorls are beautifully beaded. A number examined. 



Family NERITID^. 

 Genus XERITA Bruguiere. 



All of the species examined conformed to the following diag- 

 nosis and were similar to fig. 50 in form. 



Apex small, flat, smooth, more or less hyaline or yellowish in 

 color, consisting of one and a-half whorls rapidly increasing in 

 size. The post-nuclear whorls are strongly marked with growth 

 lines. 



The following species have been examined : 



]Verita polita Linn6. 



JVerita plicata Linne (nuclear whorls more elevated, not so flat). 



Genus IVERITIIVA Lamarck. 



Apex like that of Nerita, but whorls not so rapidly increasing. 

 The following have been examined : 



IVeritina picta Sowerby. 

 Neritiiia virginea Linne. 

 Neritina dispar Pease. 

 IVeritina meleagris Lamarck. 



A number of specimens of each species have been examined. 



