36 ANNALS NEW YORK ACADEMY OF SCIENCES 



Vulgocerithium plicatum PJiUippi 



1886. Cerithiidii plkata Philippi, Enuiu. Moll. Sicil., p. 192. 



1887. Cerithiidit rnUjatiiin Tryon, Miinual of Conch., p. 12G. 



Measurements : Length, 25.1 mm. ; greatest diameter, 1.4 mm. ; apical angle, 

 42°, changing to 24° on the last three volutions; sutural angle, 78°. 



Color : Background white, thickly mottled with yellow and golden hrown. 



The apex of the shell is much corroded, but a volution 1 mm. in diam- 

 eter shows that it possesses ribs and two spirals. The fifth volution is 

 the first to show the ornamentation plainly, and on this the spirals are 

 broad, but not greatly flattened, and the oblique-angled outline is still 

 retained. The embracing of the whorls is so great as to nearly cover the 

 lower slope of the whorl. The succeeding volutions develop a sub-sutural 

 row of nodes and the ribs are strongly defined. The upper primary 

 spirals remain always the more prominent, and the vertical element in the 

 outline of the shell disappears at about the eighth volution. The adult 

 ornamentation consists of strong ribs, which are most prominent at the 

 level of the first primary spiral, and a sub-sutural row of nodes. The 

 spirals are broad and somewhat flattened, with narrow depressions be- 

 tween them. On the body volution the ribs become narrow, crowded 

 and so low as to be nearly obsolete. The sub-sutural row of nodes is here 

 the most prominent feature of the ornamentation. 



The aperture is oval, and the callus of the inner lip is thick, with a 

 well-defined posterior tooth. The outer lip is thick and smooth, with an 

 entire margin. The anterior canal is short and widely open. 



Horizon and locality : Recent. Locality unknown. 

 No. 402.37. Columbia University collection. 



Eemakks: VuIgoceritJiium plicatum has been regarded l)y Tryon as a 

 variety of Vulgocerithium vulgatum, but it differs from that species in 

 its smaller size and in its more continuous and more prominent ribs, with 

 their most convex portion at the center of the volution instead of above 

 the center. It also has broader and more roimded spirals, and the ante- 

 rior canal is proportionally shorter. 



This species is related to the V. vulgatum group in the development of 

 the young whorls and in the general form of the shell and of the aperture. 

 The sub-sutural row of nodes and the ribs are the most noticeable features 

 of the ornamentation. 



