\l\li\l,\\l) (.liol.otlK'AL SI'RVEY 107 



and siihciiiicironii; postcriui- side very sliort; luiibones gibbous; beaks 

 (listanl and nindi incniN (•(].■" ('onrad, 1830. 



A careful e.xaniinaiioii df the vai'ious forms of Cucullaea from the 

 iMafvland ami A'irginia J'^ocene sluiws them to 1)c modific-alious of a 

 single sjiccics I hat possesses great \arial)iiil y in ninlini' and .-nrface 

 decoration. The most pi-ol'onnd dianiics appcai' upon coinjjarisoii of 

 young and adult foruis. 'J'hc immature shells are relatively not as high 

 or as tuuiid and })Ossess mucli uarrower ligament areas than the adults. 

 Eogers gave the name of C. Iran.'irrrfia to tliese young forms. Casts of 

 the larger shells are not uncommon and arc locally known as "turtle 

 heads.*' 



Professor Harris agrees with us in regarding the Maryland-Virginia 

 Cucullaeas as all of one species, and also includes in it a form from the 

 Chickasawan of Alabama of the transversa type. Dr. Dall, however, 

 recognizes two species. If it were possible to separate the forms the dis- 

 tinction between the gigantea and transversa types would be very useful, 

 since the foiiner occurs only in the Aqnia formation, while the latter 

 is the only form fonnd in the ISTanjemoy formation or in the Gnlf states. 



Occurrence. — Nan.jemoy Fokmatio?^. Popes Creek, "Woodstock, 

 Thrift (well). Aquia Foematiox. Liverpool Point, 1 mile southeast 

 of Mason Springs, Potomac Creek, Paspotansa Creek, 2 miles below Po- 

 tomac Creek, Aqnia Creek, Clifton Beach, 1 mile northeast of Piscata- 

 way. Tapper Marlboro, Hardesty, Eolph's Landing, 3 miles west of 

 Leeland, Fort Washing-ton, Glymont, Sheckel's Farm near South River, 

 Fredericktown (?). 



Collections. — Mar3'land Cleological Survey, Johns Hopkins University, 

 U. S. National Museum, Philadelphia Academy of Natural Sciences. 



Led A PAEVA (Rogers). 

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



Xacula parva Rogers, 1837, Trans. Amer. Philos. Soc, vol. v, p. 340. (Reprint 



Geology of the Virginias, 1884, p. 668.) 

 Nucula parva H. C. Lea, 1848, Proc. Acad. Nat. Sci., Phila., vol. iv, p. 102. 

 Leda parva Conrad, 18.54, Proc. Acad. Nat. Sci. Phila., vol. vii, p. 39. 

 Nuculana parva Conrad, 186.5, Amer. Jour. Conch., toI. i, p. 3. 

 Nuculana parva ConT2i6., 1866, Smith. Misc. Coll. (200), p. 3. 

 Leda parva Clark, 1895, Johns Hopkins Univ. Circ, vol. sv, p. 5. 

 Leda parva Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 83, pi. xxviii, tigs. 2a-2d 



