23 ANNALS NEW YORK ACADEMY OF SCIENCES 



two are developed from a common ancestor. This is clearly brought out 

 by a comparison of the figures of young whorls on plate vii, figs. 2, 3, 

 and plate iii, fig. 4. 



Cerithium columna Sowerby 



1855. Cerithiwin columna Soweeby, Thesaurus Conch., II, 855, pi. 178, figs. 

 55-58. 



1866. Cerithimn columna Reeve, Couch. Icon., No. 2, pi. 1, fig. 2. 



1887. Cerithium columna Tryon, Manual of Conch., IX, 123, pi. 20, figs. 17, 18. 



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

 nitz, Bd. I, Abth. 26. 85, pi. 16, figs. 7, 8. 



Measurements : Length, 29.2 mm. ; greatest diameter, 17.1 mm. ; apical 

 angle, 41° ; sutural angle, 87°. 



Color : Ground, white or cream white, with Irregular patches of dark reddish 

 brown, the amount of brown on different individuals varying greatly. 



The shell is thick and heavy, with relatively coarse spirals and narrow, 

 sharp ribs. 



The youngest volution preserved is 2 mm. in diameter. It bears two 

 strong, equal spirals with intercalated spirals of two higher orders and 

 fine spirals on the shoulder. All are crossed by ribs, which on the later 

 volutions of the shell become narrow, with wide interspaces. The orna- 

 mentation retains the same character, with an increase in the number of 

 intercalated spirals for the three succeeding volutions, after which the 

 lower of the two primary spirals becomes weaker, changing the outline of 

 the volution, as described above, from an obtuse angle to a right angle. 

 Varices occur on the later whorls to the number of about two to the 

 volution. The spirals become closely crowded just below the suture, and 

 there is a tendency toward the formation of a sub-sutural band, but it 

 never becomes well developed. On the later portion of the body volution 

 small nodes are developed on the stronger spirals. 



The aperture is broadly oval, with a well-developed posterior tooth 

 and short, oblique anterior canal. The callus of the inner lip is thick and 

 rather narrow. The outer lip is flaring and crenulated. 



Horizon and localities : Recent. Indian Ocean, Japan, Oceanica. 

 No. 20127, Columbia University collection. 



Remarks : This species is a near relative of C. menkei, differing in the 

 characters enumerated above and, like that species, reveals in its devel- 

 opment its relationship to C. tuherosum. 



