MARYLAND GEOLOGICAL SURVEY 161 



Genus CANCELLARIA Lamarck. 



Subgenus CANCELLARIA s. s. 



Cancellaria alternata Conrad. 



Plate XLIII, Figs. 1, 2, 3. 



Cancellaria alternata Conrad, 1834, Jour. Acad. Nat. Sei. Phila., voL vii, 1st ser., 



p. 155. 

 Cancellaria aUernata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 567. 

 Cancellaria alternata Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 17. 

 Cancellaria alternata Conrad, 1866, Amer. Jour. Conch., vol. ii, p. 67, pi. iv, flg. 7. 

 Cancellaria alternata Whitfield, 1894, Mon. xxiv, U. S. Geol. Survey, p. 113, pi. xx, 



figs. 5-10. 

 Merica alternata Cossmann, 1899, Essais de Paleoconch. Comp., vol. iii, p. 15. 



Description. — " Shell short siibf iisif orm ; whorls six, with nine or ten 

 thick, longitudinal, oblique eostse, with prominent spiral and finer 

 intermediate striae; spire subcorneal; aperture less than half the length 

 of the shell; labium with three plaits, decreasing in size inferiorly, as in 

 Mitra; aperture semilunar. Length, half an inch." Conrad, 1834. 



" Whorls 6, rounded, with nine or ten prominent ribs, and promi- 

 nent revolving distant striae, and an intermediate fine line ; spire conical ; 

 aperture less than half the length of the shell, sub-ovate; columella 

 3-plaited, plaits decreasing in size towards the base; umbilicus small; 

 summits of volutions flattened; 5 of the larger revolving lines on the 

 penultimate whorl." Conrad, 1866. 



"Very many specimens show six or seven prominent spiral striae, 

 while others have only the five mentioned in the description. Most 

 of them show from four to six fine raised lines on the summit of the 

 whorl, a feature not mentioned in either description, and all have 

 several other lines below the prominent ones mentioned. The form 

 of the aperture of course varies with the proportional length of the 

 shell." Whitfield, 1894. 



This species is very variable as the above descriptions show. Conrad's 

 type, which was from the Choptank formation, and the New Jersey 

 specimens have a distinct umbilicus. This feature is almost always 

 absent in the other Maryland specimens. The Jones Wharf specimens 

 differ from the others in being uniformly short, thick-set, strongly 

 ribbed, and not constricted at the suture. The specimens from the St. 

 Mary's formation approach C. lunata very closely (through intermediate 

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