THE TERTIARY FORMATIONS OF VIRGINIA. 



367 



Pecten Jeffersonius^ scallop. 



" Madisonius^ " 

 Ostrea compressirostra, mai:l 



oyster. 

 Ostrea Virginica, marl oyster, of 



small size and different shape. 

 Crassatella Marylandica, marl 

 oyster. 

 " meJina. 



Mactra delumbis. 

 " confraga. 

 " modicella. 

 Chama corticosa. 



" congregata. 

 Pectunciilus subovatus. 

 " pulvinatus. 



Perna maxillata. 

 Isocardia fraterna. 

 Artemis acetabulum. 



Area idonea. 



" stillicidium. 



" centenaria. 



" incile. 

 Venus mercenaria, 



" deformis. 



" cortinaria. 

 Astarte undulata. 



" vicina. 

 Venericardia granulata. 

 Fusus quadrieostatus. 



" parilis. 

 Fulgur carica. 

 Turritella ter-striata. 

 " alticosta. 

 " plebeia. 

 Serpula granifera. 

 Crepidula costata. 

 Buccmum laqueatum. 



Arrangement and Composition of the Eocene Strata of the Peninsula. 



But little uniformity prevails in the arrangement of these beds, as 

 observed at different localities. In general, the lowest stratum of the 

 series is of a dark greenish blue colour, and those which lie above it 

 have various shades of yellow, greenish gray and brown. In many 

 instances the upper stratum is devoid of shells, but replete with their 

 casts and impressions. Frequently it is more or less impregnated with 

 sulphates of lime, iron and alumina, which impart to it a styptic or 

 astringent flavour, and with a small amount of sulphur, recognized by 

 the odour it exhales when heated. All these ingredients, however, 

 enter into the lower beds, though in less proportion, and are not ex- 

 cluded from strata containing shells. A thin band of ferruginous 

 gravel, sometimes partially cemented, frequently overlies these beds, 

 and forms the boundary between them and the meiocene. 



We thus see a striking correspondence in the situation and condi- 



VI. — 4 R 



