Maryland Geological Survey 481 



Family CERITHIIDAE 



Genus CERITHIUM Bruguiere 

 [Encycl. Meth., pt. ii, 1792, p. 467] 



Type. — Murex aluco Linnaeus. 



Shell ratlier thick and heavy ; imperforate, multispiral; outline turrito- 

 conic, the whorls of the spire usually more or less flattened laterally and 

 regularly increasing in size ; external sculpture ornate, often varicose or 

 nodulated ; sutures distinct, closely appressed ; aperture obliquely lenticu- 

 lar, produced somewhat posteriorly, and terminating anteriorly in a short, 

 recurved, often truncate canal ; outer lip more or less expanded, and thick- 

 ened within ; inner lip excavated, usually with a denticle near the pos- 

 terior commissure and one or two plications near the anterior margin; 

 parietal wash very heavy. 



Cerithium originated before the middle of the Mesozoic, and culmi- 

 nated in the Eocene. The recent species, however, constitute one of the 

 major factors in the littoral and brackish water faunas of the temperate 

 and tropical seas. 



Cerithium tilsbryi Whitfield 



Cerithium pilsbryi Whitfield, 1893, Nautilus, vol. vii, pp. 38 and 51, pi. ii, 



fig. 3. 

 Cerithium pilsbryi Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 22. 

 Cerithium pilsbryi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 



p. 708, pi. lxxxi, figs. 3-5. 



Description. — " Shell elongated and slender; volutions numerous, num- 

 ber not determined, very gradually expanding with additional growth ; 

 apex and aperture unknown. Volutions slightly convex between the 

 sutures, and ornamented by a band of small oblique nodes immediately 

 below the suture; also by a series of larger vertical folds which extend 

 across the exposed part of the volution, below the upper band of nodes, 

 and numbering something more than half as many to the volution as the 

 nodes above. There are also very fine spiral striae, almost too fine to be 

 seen without magnifying. The lines of growth are fine but distinct, and 



Etymology: Kepa.Ti.ov, a little horn. 



