56 STUDIES IN GEOLOGY, No. 3 



irregular aperture. C. henekeni does not have the inner 

 lip shortened posteriorly. 



Only one specimen of this species occurs in the collection. 

 It is sufficiently distinct to permit its description as a new 

 species ; however, the depressed dorsal area before the pos- 

 terior canal notch may require verification through study of 

 more material, since it is possible that the shell may have 

 been deformed. Close examination of the specimen shows 

 this feature to be a possibly natural development, reasonably 

 correctable with the slight dorsal posterior depression caused 

 by the appression of the posterior inner lip, and 'it is accord- 

 ingly noted in the description as a likely natural character of 

 the shell. 



Lower Zorritos. Quebrada Zapotal. 



Superfamily CERITHIACEA 



Family CERITHIIDAE 



Genus CERiTHiUM Bruguiere 



Cerithium infranadatum n. sp. 



PLATE II Fig. 9. 



Shell large, tapering moderately, nodose, the sutures dis- 

 tinct, but slightly impressed. Whorls 10-12 in number; the 

 early whorls decorated with numerous longitudinal ridges 

 which are slightly arcuate, each with four lateral nodes 

 caused by spiral sulc'i which cross both ribs and interspaces ; 

 with the growth of the shell the longitudinal ribs become less 

 numerous and more widely-spaced ; on about the seventh 

 whorl they are larger, broader, and not so deeply cut by the 

 spiral grooves; and on the last two to four whorls they 

 center into strong, round, pustular tubercles situated below 

 the median line of the whorl, and in some specimens near 

 the base of the whorl. On the specimens examined, which 

 are badly worn, it is difficult to tell whether or not the spiral 

 sculpture continues, but lines of growth are evident. Aper- 



