MAltVLAM) (ii;()LO(iIfAr- SlUVKY G7 



TiirrUella iiototnnccimis Clark ainl Mint in. t-'lithli/vrinti Itiillouhii (\''Orh\tiny. 

 iJentaliitin iiiiniilhtriiituin (iiilih. /Jisrorliina hcrt/nloti (d'Orbiifny). 



Meretrlx Icnis (Conrnd). J'lihuuiiliiin nr/ircihi rxU (d'Orbii^ny). 



(!') Jlcretrix xubhn/ireKiM (Connid). Xonioiiina ufflnlM Heuas. 



(/) Liicinn astartiforiiih Aldricli. Am/i/iiHtfi/inii leMoiiii d'Orljiifiiy. 



Venei'lcfO'dia mdrylandica C\tirk iV Miiitiii. ('nrpulifhus marylandiciis Ilollick. 



ModioliiK maryhindicHS CluvU iiiid Martin. ''in-poUlhns marylandirns rnr. riif/tmiiH 

 Lrilii jiiiri'ii (Roiccrs). Ilollick. 



The two zones eonipri-sing the Woodstock in the Potomac area are 

 characterized as follows: 



Zone 10. — In this zone linve been placed tlie strata intervening be- 

 tween the upper layers of the Potomac Creek section and the base of 

 the Popes Creek section. The deposits are estimated to reach about 

 40 feet in thickness, and are chiefly greensands and greensand marls. 

 They appear in an nnfossiliferoiis condition in some of the ravines to the 

 west of the AYoodstock area, and along the shores where they contain a 

 few fossils of common AVoodstock species. 



Zone 17. — The highest beds at "Woodstock, and tlie Popes Creek 

 strata, are grouped together in this zone. The materials are very homo- 

 geneous, although several inconstant indurated layers appear. The 

 thickness of this zone is about 20 feet. A thin bed of Ostrea seUaeformis 

 was observed in the lower part of the zone, although evidently not 

 always at the same horizon. Otherwise, so far as observed, the fossils 

 are the same in the several parts of the two sections. The most common 

 forms are Protocardia lenis, Glycymeris idoneus, Meretrix subimpressa, 

 CorMla suhengonata, Corhula oniscus, Leda cnlteUiformis, Pecten dalli, 

 Leda improcera, Leda parva, Xucida potomacensis, Lucina dartoni, Lucina 

 'uhleri, Lucina ivhitei, and Pingicula dalli. 



LOCAL SECTIONS. 



The formations and faunal stages previously described are based on 

 the numerous local sections found scattered throughout the Eocene 

 area of Maryland. The most numerous and complete series of sections 

 is found in the valley of the Potomac river, but other and highly im- 

 portant sections are found to the northward nearly to the Delaware line. 



Potomac River Section. 

 The most complete section of the Eocene deposits of the Middle 

 Atlantic Slope is found in the valley of the Potomac river between Aquia 



