402 PROCEEDINGS OF THE ACADEMY OP [1887. 



sition here indicated accords approximately Avith the theoretical 

 position deduced from a calculation of dip and strike, using the 

 Shiloh Perna beds as an equivalent. At a height of some 350 feet 

 above the Perna beds, and consequently, at an actual depth of about 

 450 feet, occurs a stratum containing large numbers of Turritella 

 plebeia, a species, which in Maryland, incisively marks the newer 

 Miocene deposits of the State (i. e. the "Virginian"), as distinguished 

 from the older ("Marylandian"). Its presence in the position which 

 it occupies in the Atlantic City bore section would, of itself, be al- 

 most sufficient to determine the existence of a second faunal horizon. 

 The following table enumerates, as far as is known to me, all the 

 Molluscan species that have been thus far determined from the 

 Miocene formation of the State : 

 Discina luguhris, Conr. Mioc. Foss., p. 75. 

 Ostrea Virginica ( 0. Mauricensis) Gmel. 

 Ostrea percrassa, CoxiY, Mioc. Foss., p. 50. 

 Pecten Humphreysii, Conr. Bull. Nat. Inst., p. 194. 

 Pecten Madisonius, Say. Journ. A. N. S., IV. p. 134. 

 Pecten vicenarius f Conr. Proc. A. N. S., 1 . p. 306. 

 Anomia ephippiiim f L. 



Plicatula densata, Conr. Proc. A. N. S. 1. p. 311. 

 Mytilus inflatus, Tuomey and Holmes. Plioc. Foss., p. 33. 

 Mytilus incrassatus, Conr. A. J. Science, XLI., p. 247. 

 Mytiloeoncha incurva, Conr. Mioc. Foss., p. 52. 

 Lithodomus subalveatus, Conr. A. J. Conch., II, p. 78. 

 Perna inaxillata, Lam. 



Area centenaria, Say. Journ. A. N. S., IV., p. 138. 

 Area Marykmdiea, Conr. Mioc. Foss., p. 54. 

 Area subrostrata, Conr. Mioc. Foss., p. 58. 

 Area idonea f Conr. Foss. Tert. Form., p. 15. 

 Area lienosa f Say. Amer. Conch., pi. 36. 

 Peetuncuhis lentiformis, Conr. Mioc. Foss., p. 64. 

 Nucula obliqua, Say. A. J. Scieuce, II, p. 40. 

 Yoldia limatula, Say. Amer. Conch., pi. 12. 

 Astarte eompsonema, Conr. A. J. Conch., II, p. 72. 

 Astarte obruta, Conr. Journ. A. N. S., VII, p. 15. 

 Astarte jierplana f Conr. Mioc. Foss., p. 43. 

 Astarte Thomasii, Conr. Proc. A. N. S., VII, p. 267. 

 Astarte distans, Conr. Proc. A. N. S., 14, p. 288. 

 Crassatella melina, Conr. Mioc. Foss., p. 22. 



