Occasional Papers of the Museum of Zoology 81 



and guayacan. Quite independent of the nature of the under- 

 lying rocks. 



Ferussac apparently based his typical form on Lister's fig- 

 ure 2. This shows a rather small specimen with the color- 

 varices broken by a tendency towards spiral bands. The fig- 

 ure (a) of Chemnitz (vol. IX, pi. 134, fig. 1225) shows a 

 specimen with only the varices, while his figure (b) shows 

 both these and the spiral bands. 



In the series from the Dutch Leeward Islands, the color 

 variation may be analyzed as follows : 



Apex: every intergradation between pure white and quite 

 dark, lilac-blue {apiculatus) . Although both extremes com- 

 monly occur in the same locality, the colonies usually tend 

 towards a preponderance of one or the other of these color 

 forms. For instance, 97 per cent, of the specimens from 

 Bonaire have dark apices, while none of those from Aruba 

 show this tendency. Both forms are present in about equal 

 numbers in Curasao as a whole (53 per cent, white, 47 per 

 cent. blue). As a rule, the blue-tipped shells are more strik- 

 ingly banded, although some of the shells of this form from 

 Bonaire are otherwise colorless. 



Ground color: dead white in all of my specimens, but in 

 some the band- coloration is so diffuse as to tinge the last whorl 

 with light chocolate. Shells in one lot in the A. N. S. P. (no. 

 2430, collected by Raven), from Bonaire, are salmon-pink and 

 almost unicolor (ludovica) . 



Bands: in this species the spiral and growth sets of color 

 banding seem to struggle for dominancy. When present, 

 either set may be dilfuse or sharply marked, narrow or broad, 

 and may vary in color from light reddish brown to deep choco- 

 late with a purplish tinge. Ten per cent, of my specimens are 

 without bands. Nine per cent, have numerous, quite regular 

 varices, which are usually quite narrow and sharply marked. 

 This type of coloration is especially conspicuous near Land- 

 huis Hato, Curasao (Cllcd). All of the shells show a distinct 

 tendency to increase the density of the pigmentation during 

 the periods of slower growth (this, by the way, is a character- 



