1911.] NATURAL SCIENCES OF PHILADELPHIA. 439 



in the Museum of the Academy, labelled " Ecphora quadricostata, 

 .Maryland." The former of these occurs in various beds of the Chop- 

 tank formation, the latter in the underlying Calvert formation, so 

 that no more definite locality and horizon can be given than Chesa- 

 peake Miocene. 



While all of the Ecphoras are variable shells, yet in the large 

 series in the collection of the Academy this species seems detached 

 from those hitherto defined 1 by the extreme weakness of the ribs 

 in the adult stage and the sloping shoulder. The types of E. parvi- 

 costata are No. 1,514, A. N. S. P., collector unknown. 



1 See' M aryland Geological Survey, Miocene, pp. 207-211. 1904. 



