WOOD, PHYLOGENY OF CERTAIN GERITHIIDJE 47 



of the ornamentation and the form of the aperture. The nodes of the 

 sub-sutural row and of the first primary spiral have a somewhat more 

 rounded form than most species of the genus, and rows of fine nodes are 

 intercalated between them. 



A variety represented by fig. 12a, h, has the high spire characteristic 

 of the typical Yulgocerithium. 



Vulgocerithium rubiginosum Eichivald 



1830. Ccrithium ruhiginosum Eiciiwald. Naturh. Skizze von Lithauen, Vol- 



hynien u. s. w., p. 224. 

 1856. CerithUmi rubiginosum Hornes and Partsch, Abhand. der k. k. geol. 



Reichsanstalt, III, 396, pi. 41, figs. 16, 18. 



So far as caij be learned from the descriptions and figures, this little 

 species has all the characteristics of Vulgocerithium. It difl^ers from the 

 last species in the absence of the intercalated rows of fine beading, and 

 the nodes are somewhat more prominent. The species is recorded by 

 Hornes and Partsch from the Miocenic of the Vienna Basin. 



E. OLIGOGENIC AND EOCENIC SPECIES 



1. Cerithium 



The relationship between the Oligocenic and Eocenic species is so close 

 that it has been thought best to consider them together, taking up the 

 forms in the phylogenetic rather than the stratigraphic order. 



Cerithium aequispirale sp. no v. 



Plate 11, fig. 5; plate v, figs. 3, 4; plate vi, fig. 3. 



Measurements (last five volutions): Length, 23 mm.; greatest diameter, 

 10.1 mm.; apical angle. 33.5°. changing to 26.8° on the last three volutions; 

 sutural angle, 85°. 



The general form of this shell is high and narrow, with moderately 

 embracing whorls and but slightly impressed sutures. The apex of the 

 shell is broken away, and the earliest volution preserved has a diameter of 

 4 mm. and heiglit of 1.4 mm. On this volution, two spirals are stronger 

 than the others and are equal in strength. A third primary spiral at the 

 base of the whorl is partly covered by the succeeding volution. Between 

 the stronger primary spirals a secondary and two teriiary ones appear, 

 and one primary, with four secondary spirals, is above the shoulder 

 angle. This volution bears eleven strong, roimded ribs, which are well 



