MAUYLAND GKOLOGIC A I, SIUVEY 129 



others the revolviiij,' lines are nuinerous, strongly defined; lines of growth 

 smaller and much finer than the revolving lines, suture deeply im- 

 pressed, outer lip expanded, strongly nodular within, columella with 

 three folds, aperture pointed and canaliculate at base." Aldrich, 1898. 



This abundant and variable form approaches too near to some va- 

 rieties of C. graciloides to be safely separated from it. 



Length, 13 mm.; width, 8 mm. 



Occurrence. — Aquia Forjiatiox. 1 mile southeast of Mason Springs. 



Collection. — ^laryland Geological Survey. 



Caxcellaria sp. 

 Plate XXI, Fig. 2. 



Several specimens of Cancellaria were found that are so imperfect and 

 immature, that it is unsafe to describe them or even to refer them to 

 any known species, yet they are very different from our other Marj'land 

 species. 



The figured specimen represents a form from the locality two miles 

 below Potomac Creek which also doubtfully occurs at Potomac Creek, 

 and which distantly recalls C. parva Lea.^ When the adult is found 

 it will probably be recognized as a new species. 



Another form from Potomac Creek may be C. ulmula Harris' or a 

 variety. This is so imperfect that it does not seem desirable to figure it. 



Occurrence. — Aquia Foematiox. 2 miles below Potomac Creek, Po- 

 tomac Creek. 



Collection. — Maryland Geological Surrey. 



Subgenus NARONA H. and A. Adams. 



Cax-cellaeia (Xaeox'a) potomacex'Sis n. sp. 



Plate XXI, Figs, 3, 3a. 



Description. — Shell elongate; mouth more than half the length of the 



sheU; spire short; whorls marked with distinct, raised, flat-topped, re- 



volying ridges, with interspaces twice as broad; body whorl with twenty 



of these ridges, whorls of the spire with six. Lines of growth and 



iContrib. Geol.. p. 42, pi. v, fig. 141. 



sProc. Acad. Nat. Sci. Phila., vol. xlrii, 1895, p. 66, pi. tI, fig. 6. 

 9 



