1914.] NATUFAL SCIENCES OF PHILADELPHIA. 209 



FEESH-WATER MOLLUSKS OF THE OLIGOCENE OF ANTIGUA. 

 BY AMOS P. BROWN AND HENRY A. PILSBRY. 



In a recent paper by one of us^ reference has been made to the 

 deposits carrying these fresh-water shells, which were first noted by 

 Nugent.- His collection of iVntigua fossils, including, no doubt, speci- 

 mens of these fresh-water moUusks, is still preserved in the collections 

 of the Geological Society of London, now in the British Museum. 

 These deposits- were later described by Purves^ as his division E, 

 under the name of the "Lacustrine or fresh-water chert." These 

 beds are mapped by Purves as extending completely across the 

 island, in the central plain from Corbizon Point and Dry Hill in the 

 northwest to near Willoughl)y Bay and Falmouth Harbor in the 

 southeast. His observations on the fossils appear to have been 

 made at Dry Hill and at Corbizon Point. M. Purves records the 

 following genera as occurring in these cherts: Melania, Zonites, 

 Nematura or Amnicola, Planorhis, Melampus, Neritina, Truncatella, 

 Pomatias. He also states that the specific descriptions of these 

 shells will be published later, but this seems never to have been done. 



The species described in this paper were collected from the sea 

 cliffs at Dry Hill, where these flinty beds, carrying fresh-water species, 

 outcrop on the seashore and where they have weathered out by the 

 action of the rains and the salt water dissolving away the calcareous 

 material and leaving the silicified shells intact in a remarkably good 

 state of preservation. When these beds were seen inland at several 

 points, the weathered surfaces of the layers exposing the shells were 

 not so well preserved as at Dry Hill or at Corbizon Point, on'.y 

 sections being found in most cases, as the shells were imbedded in 

 the compact flint. . This Avas, of course, the case at the two localities 

 above noted, likewise; the hard, compact flint layers, varying in 

 thickness from one to four inches, being frequently crowded with 

 these fresh-water shells that showed only in sections upon the frac- 



1 Brown, Notes on the Geology of the Island of Antigua, Proc. A. N. S. P., 1913, 

 pp. 58-4-816. See also p. 596 of the same paper. 



2 Nugent, A Sketch of the Geoiogv of the Island of Antigua, Trans. Geol. Soc. 

 London, ser. 1, Vol. V, (1821), pp.. 459-47.5. 



3 Esquisse geologique de I'lle d'Antigoa, Bull. Mus. Roy. Hist. Nat. Belg., 

 Vol. Ill, 1884-85, pp. 273-318. 



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