24 ANNALS NEW YORK ACADEMY OF SCIENCES 



Cerithium citrinum mut. bicolor Hombron et Jacques 



« 



1842-1853. CerithiiiiH bicolor Hombron et Jacq. Voyage au Pole Sud., pi. 23, 

 figs. 14, 15. 



1887. Cerithium citrinum Tryon. Manual of Conch., 123, pi. 2, fig. 22. 



1898. Cerithium citrinum Kobelt, Syst. Conch.-Cabinet von Martini u. Chem- 

 nitz. Bd. I, Abth. 26, 111. 



Measurements : Length, 29.7 mm. ; greatest diameter, 16.3 mm. ; apical 

 angle, 44°, changing to 3U° on the last three volutions ; sutural angle, 86°. 

 Color: Cream white with patches of a slightly darker yellowish tone. 



The first two of the volutions preserved are precisel}' similar to those 

 of Cerithium citrinum. On the third volution the ribs become con- 

 tracted, leaving broad interspaces, as in C. columna, but the spirals retain 

 the characteristic development of C citrinum — that is, bundles of spirals 

 with deep grooves between them. This type of ornamentation is carried 

 still farther on the mutation bicolor, until, as early as the seventh volu- 

 tion, the interspaces are smooth and nearly or quite as wide as the groups 

 of spirals themselves. The upper of the two primary spirals becomes 

 slightly stronger than the lower as early as the fourth volution, and the 

 two retain the same relative strength for seven volutions. The eighth 

 volution attains the angular outline characteristic of C. columna. All 

 the spirals of this form are j^rominent and sharply defined, even more 

 so than on either C. citrinum or C. columna. On the body volution all 

 the strong spirals break up into fine nodes. 



The aperture is broadly oval, with a posterior tooth and short, oblique 

 anterior canal. The outer lip is strongly crenulated. The callus of the 

 inner lip is strong and not closely applied to the surface of the shell. 



Horizon and locality : Recent. Philippines. 

 No. 20129, Columbia University collection. 



Eemarks: This shell has the prominent shoulder of C. columna, while 

 retaining the thin shell, fine sculpture and development of spirals char- 

 acteristic of C. citrinum. 



Cerithium scabridum Reeve 



1866. Cerithium scahridum Reeve, Conch. Iconica, XV, No. 52, pi. 8, fig. 52. 



1887. Cerithium cotumna mut. scahridum Tbyon, Manual of Conch., IX, 123, 

 pi. 20, fig. 20. 



1898. Cerithium scahridum Kobelt, Syst. Conch.-Cabinet von Martini u. Chem- 

 nitz. Bd. I. Abth. 26. 210, pi. 37. fig. 6. 



Measurements : Length. 20.5 mm. ; greatest diameter, 11.4 mm. ; apical 

 angle. .34.5° ; sutural angle. 82.5°. 



Color: White with the more prominent spirals sparingly touched with 

 brown. 



