WOOD, PHYLOGENY OF CERTAIN CERITHIIDJE 25 



The youngest volution preserved probably corresponds with the fourth 

 volution of C. 77ienJcei, being 2 mm. in diameter. This volution has two 

 strong, equal spirals and three intercalated ones. The shoulder has five 

 and the lower slope of the whorl one additional spiral. Eibs are present 

 to the number of eleven on this volution. The ornamentation resembles 

 that of Cerithium citrinum in Ijeing made up of bundles of fine spirals, 

 but the depressions between the groups are less deeply carved than in 

 that species. The two primary spirals remain equal for five volutions, 

 .after which the outline of the volution becomes angular, but not sharply 

 so as in C. menkei. On this shell, as usual in this group, it is the upper 

 of the primary spirals which is most prominent. The ribs become weaker 

 on the body volution and disappear on the later portion of it. On this 

 portion of the shell, also, all the coarser spirals break up into rows of 

 •small nodes. A large varix is present on the side of the body volution 

 opposite the aperture. 



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

 narrow callus and short anterior canal. The outer lip is finely crenu- 

 lated by the spirals of the outer surface and not flaring. 



Horizon and locality : Recent. Both Reeve and Kobelt report the locality 

 of the species as unknown. The specimens in the collection of Columbia Uni- 

 versity referred to this species are from the Bird Islands, Pacific Ocean. 



No. 20130, Columbia University collection. 



Eemaeks: This little shell is nearest to C. citrinum, but it differs in 

 its smaller size, white color, less deeply carved surface ornamentation, 

 the more angular outline of the volutions and the short anterior canal. 

 From the mutation hicolor, it differs in size and color and in the less 

 prominently developed shoulder. 



Cerithium mediterraneum Lamarck 



1843. Cerithium mediten-aneuin Lamarck. Animaux sans vert., IX, 813. 

 18.55. Cerithium mediterraneum Sowerby. Thesaurus Conch., II. 865. pi. 178, 



fig. .50; pi. 101, figs. 128. 131-13.3. 

 1866. Cerithiimi mediterraneum Reeve, Conch. Icouica, XV, No. 53. 

 1887. Cerithium rupestre Tbyon, Manual of Conch., IX, 126, pi. 21, fig. 48. 



Measurements : Length, 25 nun. ; greatest diameter, 12.4 nun. ; apical angle, 

 39.8°, changing to 25° on the seventh volution : sutural angle, 77.5°. 



Color : Cream white, mottled with streaks of yellow or brown. Color bands 

 usually passing transversely across the spirals, but when parallel with them 

 seeming to occupy the depressions between the spirals rather than their more 

 •convex portions. 



The youngest volution preserved is .9 mm. in diameter. This volution 



