MARYLAND GEOLOGICAL SURVEY 615 



M.ODIOLUS BURLINGTONENSIS WMtfield 



Modiolus burlingtonensis Whitfleld, 1885, Mon. U. S. Geol. Survey, vol. ix, 



p. 65, pi. xvii, figs. 8, 9. 



Modiolus burlingtonensis Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. 

 Modiolus burlingtonensis Weller, 1907, Geol. Survey of New Jersey, Pal., 



vol. iv, p. 505, pi. Iv, figs. 18, 19. 



Description. " Shell of moderately large size, very ventricose, and with 

 subparallel dorsal and ventral margins, large prominent umbones and 

 incurved beaks situated near the anterior end but not terminal, the 

 anterior margin perceptibly extending beyond them and rounded. 

 Umbonal ridge prominent and subangular, especially near the beaks, and 

 becoming broader and more rounded posteriorly; surface of the valves 

 strongly constricted and sinuate in front of the ridge and the anterior 

 surface again inflated: cardinal slope comparatively broad and slightly 

 concave toward the postero-cardinal border. Hinge line straight and 

 three-fifths as long as the shell, and rather strongly impressed in the 

 internal cast ; postero-cardinal margin rounding rapidly forward from the 

 more narrowly rounded posterior extremity. Surface of the cast, the only 

 condition under which it is known, apparently smooth or marked only by 

 irregular concentric lines of growth, some of which produce undulations 

 of considerable strength on the casts. On one individual there appear 

 on the posterior cardinal slope very faint indications of rather coarse 

 radiating lines, but too faint to warrant the statement that such markings 

 really existed on the shell." Whitfield, 1885. 



Type Locality. Burlington County, New Jersey. 



The species is much the largest of any of the Matawan Modioli, and is 

 represented in Maryland by only a couple of imperfect casts. 



Occurrence. MATAWAX FORMATION. Camp U & I, opposite Post 192, 

 Chesapeake and Delaware Canal, Delaware. 



Collection. Maryland Geological Survey, Philadelphia Academy of 

 Xatural Sciences. 



Outside Distribution. Matawan Formation. Merchantville clay marl, 

 New Jersey. 



