MARYLAND GEOLOGICAL SURVEY 675 



species, however, it lacks the radiating ribs usually impressed upon the 

 posterior slope of C. perelongatum, and the anterior muscular scar is not 

 so low in position. 



" In the collections of the National Museum at Washington this species 

 is represented by numerous examples from the South, which have usually 

 been referred to C. dumosum. These southern specimens are perfectly pre- 

 served shells which are smaller than the usual examples from the Tinton 

 beds in New Jersey, but their surface markings are identical with those 

 of the type specimen. The species differs from C. dumosum in its more 

 elongate form and in the much coarser surface markings. C. tippana is 

 another allied form in which the surface markings are fully as coarse as in 

 C. kiimmeli, but there is only a single row of smaller tubercles between 

 the larger ones in that species, instead of two as in C. kummeli." 

 Weller, 1907. 



Type Locality. Beers Hill Cut, New Jersey. 



The casts of C. Tcummeli are characterized by higher, more acute 

 umbones than those of either C. dumosum or C. tenuistriatum. It is 

 further differentiated from C. dumosum by the relatively higher altitude, 

 the less equilateral outline and the more prominent anterior adductor 

 muscle scar. 



Occurrence. MATA WAIST FORMATION. Camp Fox, Post 236, Post 218, 

 Camp U & I, Post 196, one-eighth of a mile west of Summit Bridge, 

 Chesapeake and Delaware Canal, Delaware; 1 mile west of Chesterfield, 

 Anne Arundel County, Maryland. MONMOUTH FORMATION. Two miles 

 west of Delaware City, on John Higgins farm, DelaAvare; Brooks estate 

 near Seat Pleasant, 1 mile west of Friendly, Prince George's County, 

 Maryland. 



Collections. Maryland Geological Survey, New Jersey Geological Sur- 

 vey, U. S. National Museum. 



Outside Distribution. Monmouth Formation. Navesink marl, Tinton 

 beds, New Jersey. Ripley Formation. Exogyra costata zone, Eufaula, 

 Alabama; Quitman, Union and Tippah counties, Mississippi. Extreme 

 top of zone, Pataula Creek, Georgia; Barbour and Henry counties, Ala- 

 bama. 



