83 THE GEOLOGY OF CALVERT COUNTY 



zones. Of these, Zone 17 is the lower one. The material composing 

 this stratum is mostly yellow sand along the Calvert CliflEs. It is 

 almost entirely composed of fossils, the yellow sand simply filling in 

 the spaces between the organic remains. The fauna of this zone is 

 extremely large, but the following will suffice to give an idea of some 

 of the types: 



Ecphora quadricostata, Turritella plebeia, Panopea americana, 

 Corl)ula idonea, C. cuneata. Metis hiplicata, Macro call ista marylandica, 

 Venus mercenaria, V. campecJnensis var. cuneata, Dosinia acetahidufii, 

 Isocardia fraterna, Cardium laqueatum, Crassatellites turgidulus, Astarte 

 tliisphila, Pecten coccymelus, P. madisonius, Melina maxillata. Area 

 staminea, etc. 



This zone makes its appearance along the Calvert Cliffs at Parker 

 Creek, where it is about 6 feet in thickness, and is continuously exposed 

 until it dips beneath tide a little north of Flag Pond. It may also 

 be seen at various points on the Patuxent Eiver. It appears to thicken 

 considerably southwestward along the strike, for where best exposed 

 on the Patuxent Eiver it is at least 18 feet thick near the mouth of 

 St. Leonard Creek and ovei 30 feet thick at Drum ClifE, in St. Mary's 

 County. This zone corresponds to " Zone e " of Harris.' 



Zone 18. — This zone is for the most part unfossiliferous, although 

 in places it carries some imperfect fossils and fossil casts. The mate- 

 rial of which it is composed is for the most part yellowish sand above 

 but grades down into bluish clay below and at times the entire stratum 

 is composed of bluish clay. In tliickness it varies from 18 to 22 

 feet aloUig the Calvert Cliffs, where it is continuously exposed from 

 Parker Creek to a point a few miles south of Flag Pond. Where this 

 zone is exposed at Drum Cliff it is thinned down to about S feet in 

 thickness. 



Zone 19. — This constitutes the upper of the two great fossiliferous 

 zones of the Choptank formation. Like Zone 17 it is composed almost 

 entirely of fossils with the interstices filled with reddish and yellow 

 sand. It varies in thickness from 12 to 15 feet along the Calvert Cliffs 



' Loc. cit. 



