150 SYSTEMATIC PALEONTOLOGY 



This form is very abundant in the Kanjemoy formation, and occurs 

 near the top of the A quia formation at Upper Marlboro, in the indurated 

 ledge and just above it, and also in the same bed near South Eiver bridge. 



Length, 30 mm.; width, 10 mm. 



Occurrence. — JSTanjemoy Foemation. Popes Creek, Woodstock. 

 Aqijia Foemation. Upper Marlboro, Sheckels Farm near South Eiver. 



Collection. — Maryland Geological Survey. 



Family VERMETIDAE. 



Genus VERMETUS Adams. 



Veemetus sp. 

 Plate XXVII, Figs. 5, 5a, 6, 7. 



Vermetus sp. Clark, 1895, Johns Hopkins Univ. Circ, vol. sv, p. 4. 



Vermetus sp. Clark, 1896, Bull. 141, U. S. Geol. Survej^, p. 71, pi. siv, figs. 2a, 2b. 



Description. — Fragmentary masses of this form are found at various 

 points in the Potomac Eiver region, but no specimen sufficiently well 

 preserved for specific determination has been obtained. The fragments, 

 however, probably represent a new species. The form is characterized 

 by longitudinal furrows, giving it a somewhat angulated appearance, and 

 by transverse, scaly lines interrupted by the furrows. The average 

 diameter of the tubes is about 3 mm. 



Occurrence. — Aquia Foemation. Piscataway Creek, Potomac Creek, 

 Eolph's Landing, Upper Marlboro. 



Collections. — U. S. National Museum, Johns Hopkins University, 

 Maryland Geological Survey. 



Family NATICIDAE. 



Genus NATICA Lamarck. 



Natica cliftonensis Clark. 



Plate XXVIII, Fig. 1. 



Natica cliftonensis Clark, 1895, Johns Hopkins Univ. Circ, vol. xv, p. 4. 



Natica cliftonensis Clark, 189(5, Bull. 141, U. S. Geol. Survey, p. 09, pi. xii, fig. 4. 



Description. — " Shell small, with four or five whorls; spire low; body 

 whorl much inflated; suture well marked; surface smooth, except for 

 lines of growth; aperture large, with thick callus." Clark, 1896. 



