MARYLAND GEOLOGICAL SURVEY 259 



Calliostoma eboreum (Wagner). 

 Plate LXI, Fig. 7. 



Trochus eborens Wagner, 1839, Jour. Acad. Nat. Sci. Phila., voL viii, 1st ser., p. 

 52, pL ii, fig. 5. 



Monilia (Leioirochu/i) eborea Conrad, 1863, Proc. Acad. Nat. Sci. Phila. vol xiv 

 p. 569. ' ' ' 



Monilea (Leiotrochus) eborea Meek, 1864, Miocene Check List, Smith. Misc Coll 



(183), p. 1.5. 

 Turbo eboreus Heilprin, 1887, Proc. Acad. Nat. Sci. Phila., vol. xxxix, pp. 399, 404. 

 Calliostoma eboreum Dall, 1893, Trans. Wagner Free Inst. Sci., vol. iii, pt. ii, p'. 398. 

 Monilea (Leiotrochus) eborea Whitfield, 1894, Mon. xxiv, U. S. Geo!. Survey,' p. 13.5, 



pi. xxiv, tigs. 7-10. 



Description.— '' ^\\e\\ smooth and slightly polished; spire short, coni- 

 cal; whirls flattened laterally, margined above by a very obtuse obsolete 

 carina ; spiral lines obsolete ; periphery sharply angulated, subcarinated ; 

 base flattened; subimibilicated columella grooved; aperture half the 

 length of the shell." Wagner, 1839. 



Dr. Dall says in regard to this species: "This species is a typical 

 Calliostoma, with a rather angular periphery which forms a line over the 

 suture below it, a polished surfac**, mostly smooth, with a few fine but dis- 

 tinct, elevated spiral threads, rather irregularly disposed and sometimes 

 absent. The base is generally smooth, flatfish, imperforate, with the 

 u.mal arched pillar ending m an obscure projection (common to the 

 genus) and a few spiral threads about the umbilical region. Old speci- 

 uiens ha\e the last whorl less angular at the periphery, the base rounded 

 and the aperture less quadrate than in smaller specimens. The threading 

 is irregular and occasionally profuse or entirely absent." 



This species may readily be confused with C. wagneri and C. aphdium. 

 It is possible that the latter is the normal form of the adult. 



Height, G mm. ; diameter, 6.5 mm. 



Occ^Hvmce.— Choptank Formation. Jones Wharf. Calvert For- 

 mation. 3 miles south of Chesapeake Beach, Eeed's, Westcott Farm 

 near Church Hill. 



Collections.— dryland Geological Survey, U. S. National Museum, 

 Wagner Free Institute of Science. 



