160 SYSTEIMATIC PALEONTOLOGY 



Thin, polished, slightly arched; much contracted near the anterior 

 extremity; anterior opening suhcircular, posterior simple. 



This species differs from C. subcoarctatus Gabh in having the con- 

 striction hegin much nearer the aperture. There is no longitudinal 

 striation. 



Length, 8 mm.; width, 1.25 mm. 



Occurrence. — NajSTJemoy Foemation. Woodstock, Head of ISTanjemoy 

 Creek, East and west of Port Tobacco, H and 2 J miles above Popes 

 Creek, 1 mile southeast of Piscataway, Upper Marlboro (deep cut near 

 Chesapeake Beach E. E. station), Well at Chesapeake Beach (90-92 

 feet). -Aquia Pormatio^". Aquia Creek, Liverpool Point, Clifton 

 Beach, 1 mile northeast of Piscataway. 



Collection. — Maryland Geological Survey, Johns Plopkins University. 



Class PELECYPODA. 

 Order TELEODESMACEA. 



Family TEREDINIDAE. 



Genus TEREDO Linne. 



Teeedo vieginian-a Clark. 



Plate XXX, Figs. 1, la, 2, 2a, 3. 



Teredo virginiana Clark, 1895, Johns Hopkins Univ. Circ, voL xv, p. 5. 



Teredo virginiana Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 72, pi. xv, ligs. 5a-5c. 



Teredo virginiana Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, part iv, p. 813. 



Description. — " Shell unknown; tube thick, cylindrical, irregularly 

 curved, rapidly tapering; surface smooth, or with fine lines of growth; 

 prominent transverse segment near posterior extremity of the tube in 

 some of the forms." Clark, 1896. 



This type compared with the forms described from the Alabama Ter- 

 tiary shows various points of dissimilarity, and even in the absence of 

 the valves seems, from its common occurrence, worthy of a name. 



The tubes often occur in large masses in pieces of lignite. 



Diameter of tube (maximum), 5 mm. 



Occurrence. — Xanjemoy FoEiiATiON, \ mile below Chapel Point. 

 Woodstock, ITills Bridge, West of Port Tobacco, Ujiper Marlboro (deep 



