WOOD, PHYLOGENY OF CERTAIN CERITHIIDM 39 



extreme sharpness of the principal row of nodes, which give the volution 

 a distinctly angular outline. The sub-sutural row of nodes is less well 

 defined than on V. vulgatum. 



The species is distinguished from V. pluatuvi and V. gracile by its 

 sharp nodes and the greatly flattened sjjirals. 



B. PLEISTOCENIC SPECIES OF VULGOCERITHIUM 



Vulgocerithium vulgatum 



M. Cossmann figures, on plate ;}, fig. 14, of his Essais de Paleconcho- 

 logie, a specimen from the Pleistocenic of Saix, which he refers to this 

 species. It is smaller than the normal recent individuals, and the nodes 

 of the principal row are prominent and somewhat widely spaced. 



C. PLIOCENIC SPECIES OF CERITHIUM 



No specimens of the Ceritliium tube7'osum group from the Pliocenic of 

 the Eastern Hemisphere are available for study, and the information fur- 

 nished by the literature is meager. 



Ceritliium crenatuni Buoccni, figured in Quenstedt's Petrefaktenkunde 

 Deutschlands, plate 204, fig. 46, is of a small specimen from the Pliocenic 

 of Asti, which may belong in this group. It has the oval aperture, pos- 

 terior tooth, and crenulated outer lip of Cerithium sens. str. It also has 

 in the young stages two rows of nodes which are stronger than the others, 

 but in the absence of specimens it is impossible to be sure that it is cor- 

 rectly placed here. 



In the American Pliocenic several species occur which apparently be- 

 long in this group. Of these only two actual specimens were obtainable, 

 but good figures and descriptions aid in determining the relationaship of 

 others. 



Cerithium callisoma Dall 

 Plate VII, fig. 1 ; plate viii, figs. 1, 2 ; plate ix, fig. 1. 



1892. Ceritliium vaUisoma Dall, Trans. Waguer Free Institute of Sci., Ill, 

 pt. 2, 282, pi. 14, fig. 8. 



Measurements : Length, 20.8 mm. ; greatest diameter, 8 mm. ; apical angle, 

 35°, changing to 26° on the last three volutions; sutural angle, 80°. 



The youngest volution preserved on the specimens studied is .4 mm. in 

 diameter and has three spirals, of which the two lower are equal in size 

 and stronger than the upper one. Eibs are also present at this stage. 



