MAUVI.AM) (IICOI.OGICAL SURVEY 149 



This species apparently never reaches tiic (liineiisicjiis of T. moiioni, 

 but is cDiiiiiKiiily associalcd with it. Tiike T. morloni, it is largely con- 

 fined to the Paspotansa mernher of the A(|iiia I-'orinatioii. 



Length, 140 mm.; width, 25 mm. 



Occurrence. — Aquia Formation. I'Ort Washington, Clifton Beach, 

 A([uia Creek, 1 mile soul ln'asl of .Mason Springs, Glyniont, Mouth of 

 Paspotansa Creek, 1 mile noi-theast of Piscataway, Near Annapolis, Be- 

 tween Bnena Vista and Collington, Tinkers Creek, Liverpool Point, 

 Upper Marlboro, Sheckels Farm near South Eiver, Brooks Estate near 

 Seat Pleasant. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum, Philadelphia Academy of Natural Sciences. 



-TUERITELLA POTOMACENSIS n. sp. 



Plate XXVII, Figs. 2, 3. 



Description. — Shell slender, elongate; whorls many; each whorl cari- 

 nated at the base, diminishing sharply in diameter toward the apex, and 

 concave in the middle; sculpture consisting of one or two strong, ele- 

 vated cariuae at the base of the whorl, and about five moderately strong 

 ones, irregularly spaced above them, and between these secondary alter- 

 nating threads and fine, raised, revolving lines; some of the carinae, 

 especially those toward the middle of the wdiorl, are beaded. 



Length, -iS mm.; width. 10 mm. 



Occurrence. — Xaxjemoy Foematiox. Popes Creek, Woodstock. 



Collection. — Mar^dand Geological Survey. 



Genus MESALIA Gray. 



Mesalia obeuta (Conrad). 



Plate XXA^II, Fig. 4. 



TuvrUeUa ohruta Conrad, 1833, Fossil Shells of the Tertiary, Xo. 4, p. 45 ; No. 3 



[3ud Edit.], lSo.5, p. 40. pi. xv, fio-. 12. 

 Turritella veuusta Conrad, 1835, Trans. Geol. Soc, Penn., vol. i, p. 336. 



Description. — "Subulate, with about eleven slightly convex volutions, 

 with about seven sharp elevated striae on each, and intermediate fine 

 crowded lines; space about the suture indented." Conrad, 1833. 



