MAHVi.AM) (;i;()i.<)(;i( Ai. sritvi;v 185 



Tho spii'c is usually i)erruriite, and the ix'vulviujf lines alternate and 

 jiunctatc. It most closely resembles C. nhlrirlil Lan<;don, i'ntm which it 

 is distiii^uislied hv hcin;^- |ii()|M)rli(tnMlly lon;.M'r, less cylindrical in out- 

 line, and witli tlic spii-c less stfoii;^ly |ici'riii'ati'. 



JA'n<,dh, 1 mm.; width. ;{..") mm. 



Occurrence. — Xanjemoy Formation. West of I'lirt Toljacco, Head of 

 Nanjemoy Creek, Woodstock. Aquia Formation". 1 mile southeast 

 of Mason Si)rin<:s, Potomac Cicek, 2 nnles below Potomac Creek, 1 

 mile northeast of Piscataway, Clifton Beach. 



Colleclioits. — Johns Hopkins University, ^^Taryland Geological Survey. 



Supertamilv TOXOGLOSSA. 

 Family I^LHUROKJMIDAE. 



Genus PLEUROTOMA Lamarck. 



Pleurotoma HARRIS! Clark. 

 Plate XX. Figs, o, 5a, G. 



rieurotorna hnrrisi Clark, lsfl.5, .Jolins Hopkins Univ. Circ, vol. .vv, p. 4. 

 Pleurotoma /(urrisi Clark, 189(5, Bull. 141, U. S. Geol. Survej-, p. 64, pi. ix, figs. 4a, 

 4b. 



Description. — '' Shell of moderate size, elongate, five or six whorled; 

 surface with distinct, revolving lines of varying size, crossed by trans- 

 verse ridges; aperture narrow, with long straight canal." Clark, 1896. 



The lower half of the whorl is strongly convex and is strongly orna- 

 mented with revolving lines, alternating in size, and is crossed on the 

 shonlder by oblique nodular ridges. The upper half of the whorl is 

 flat, with very faint revolving lines, except one or two .strong ones about 

 the middle of the flat zone. The 'aperture narrows rapidly toward the 

 base, the body whorl partaking of the constriction. The canal is very 

 long, straight, and narrow. 



Length, 30 mm.; width, 8 mm. 



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

 tomac Creek. 1 mile southeast of Mason Springs. 



Collection. — Marvland Geolosical Survev. 



