Modification of the Apex in Gastropod MollusJcs. 703 



These two species have a flat nucleus of one and a-half whorls, 

 similar in form to fig. 50, excepting that all the whorls are 

 smooth. They are yellowish or brownish in color. A number 

 of specimens of each species have been examined. 



Family NATICIDJE. 

 Genus NATICA Lamarck. 

 The nuclear whorls of all the species of this genus seem to 

 conform to the following diagnosis : Apex small, smooth, rounded, 

 polished, consisting of one and a-half narrow, rapidljr increasing 

 whorls. Color variable. The following species have been ex- 

 amined (fig. 56) : 



jVatica lineata Chemnitz (dark horn). 

 IVatica vitellus Lamarck (yellowish). 

 ]¥atica alapapilionis Chemnitz (hyaline). 

 Natica adansonii Eecluz. (hyaline). 

 ]yatica niaroccana Dillwyn (hyaline). 

 JVatica mamilla Linne (white). 

 Natica lamarckiana Eecluz. (pinkish-horn). 

 Natica opaca Eecluz. (white). 

 IVatica canrena Lamarck (hyaline). 

 IVatica heros Say (blackish). 

 Xatica duplicata Say (bluish or whitish). 

 IVatica labrella Lamarck [two whorls, hyaline). 

 IVatica bebraea Mart, ^yellowish). 

 IVatica flemingiana Eecluz. (two whorls, white). 

 IVatica conicus Lamarck (two whorls, hyaline). 



A large number of specimens have been examined. 



Family TROCIIIDJE. 

 Genus CAL,L,IOSTOMA Swainson. 

 Calliostoiua langieri Philippi. ( Fig. 57. ) 



Apex small, rounded, shining, rapidly increasing, consisting of 

 one and a-half whorls. The first half whorl is smooth and the 

 second whorl is encircled by several (four or five) heavy spiral 

 lines. The post-nuclear whorls are at first encircled by granular 

 spiral ridges, which soon become smooth. On the last whorls 

 the spaces between the ridges become impressed. Two speci- 

 mens examined. 



