WOOD, PHYLOGENY OF CERTAIN CERITHIIDM 57 



2. Vicinocerithium 

 Vicinocerithium parallelum gen. et sp. nov. 



Plate VII, figs. 4, 5 ; j^late viii, figs. 4, 5 ; plate ix, figs. 3, 4. 



Measurements : Length, 29 nmi. ; greatest diameter, 12 mm. ; apical angle, 

 30.5° ; sutural angle, 81.5°. 



The protoconch of this species is not preserved. The youngest volu- 

 tion present bears three spirals, the lowest of which is the most promi- 

 nent, and is separated by a wide interspace from the two upper spirals. 

 On the next volution ribs appear, and the median spiral becomes stronger 

 than the upper, but not quite so prominent as the lowest spiral. A slight 

 ridge below the suture forms a fourth ill-defined spiral. On the third 

 volution present the two lower spirals are equal in strength, and a fine 

 spiral is intercalated between them. The third spiral has also become 

 stronger, so that the outline of the volution is a regular curve. Two ad- 

 ditional fine spirals appear just below the suture. The fourth and fifth 

 volutions are essentially like the third, with an increase in the number of 

 fine spirals. On the sixth volution the median primary spiral becomes 

 stronger than the other two, and this tendency increases until, on the 

 adult whorls, this spiral forms the margin of a sharply angled volution, 

 with numerous fine spirals on the shoulder and the lower slope of the 

 whorl. The uppermost primary spiral is reduced to the rank of a sec- 

 ondary spiral, and the lowest primary spiral, originally the strongest on 

 the shell, is much reduced in relative size, though still stronger than the 

 secondary spirals. This and another strong spiral just above the suture are 

 crenulated, showing a tendency toward the formation of nodes, which on 

 the latest portion of the body volution are fairly well developed. A third 

 nodose spiral is present below those just described, and fine spirals are 

 intercalated between all coarser ones on the lower slope of the body 

 volution. 



The aperture is nearly circular and the anterior canal is rather long 

 and widely open. The outer lip is thin and the inner lip is covered by a 

 strong callus. 



Horizon and locality : Sables Moyens. Le Guepelle, Paris Basin. 

 No. 20156, Columbia University collection. 



Remarks : This species has been considered identical with Cerithium 

 (VicinocerWnum) houei Pesh., and if the adult characters alone are 

 considered, they are hardly distinguishable, the only difference being that 

 the present species has a somewhat higher spire and the shoulder is far- 



