MARYLAND GEOLOGICAL SURVEY 



79 



ntella plebeia, T. variabilis, Polynices heros, Corbula inequalis, Pecten 

 jeffersonius, Area idonea, etc. This stratum is about 14 feet in thick- 

 ness. It corresponds to " Zone g " of Harris.'' 



Zone 23. — This zone is composed of drab clay and sand. It has suf- 

 fered considerably from erosion, but along the Calvert cliffs it carries 

 some fossils of which Turritella plebeia is the most important. It shows 

 a thickness of 30 feet, but is unconformably overlain by the Pleistocene 

 sands and gravels. 



Zone 24. — A break in the stratigraphic continuity of the St. IMary's 

 formation occurs south of Drum Point and the e.xact relation of this 

 zone to those preceding is not definitely Imown. It is believed, how- 

 ever, to lie very close to Zone 23. At Chancellor Point on the St. Mary's 

 Eiver, where it has been studied, 15 feet of bluish sandy clay are ex- 

 posed, overlain unconformably by Pleistocene loams. At this place a 

 large number of fossils are present, of which the following may be 

 mentioned: Aceteon ovoides, Retusa marylandica, Terebra curvilirata, 

 Conus diluvianus, Surcula engonata, Fulgur fusiforme, Turritella varia- 

 bilis, Panopea goldfussi, Callocardia sayana, Yeniis campechicnsis var. 

 mortoni, Isocardia fraterna, Phacoides anodonta, Pecten madisonius, 

 P. jeffersonius, etc. 



LOCAL SECTIONS. 

 I. Section at Drum Cliff near Jones Wharf. 



Reddish yellow loam, sand, and gravel 



fGreenish clay containing poorly preserved remains of 

 Balanus concavus, Panopea americana, Phacoides 

 contractus, Cardium laqueatum, Pecten madisonius, 

 Ostrea carolinensis, etc. iZone 19, in part) 



Greenish unfossiliferous clay (Zone IS) 



Brownish and greenish fossiliferous sand ijartially 

 indurated above, solidified to solid rock at base, 

 carrying the following species : Balanus concavus, 

 Ecphora guadricostata var. umbilicata, Turritella 

 plebeia, Corbula idonea, Macrocallista marylandica, 

 Dosinia acetabulum, Cardium laqueatum, Crassatel- 

 lites turgidulus, Astarte thisphila, Pecten madi- 

 sonius. Mclina maxillata. Area staiiiinca, Scutella 

 abcrti, etc. (Zone 17. in part) 



Feet. Inches. 



Total 



