CAPE COD GEOLOGY 



31 



the New England Islands, all these fossiliferous beds were usually referred to a 

 post-Pliocene date. For a time, indeed, Dana regarded the deposit at Sankaty 

 Head as postglacial. Recent work has shown that certain deposits of sand con- 

 tain extinct species as old as Pliocene. One such deposit lies near Southampton, 

 on Long Island, and one was found in the cliffs at Gay Head, on Marthas Vine- 

 yard. At both places Miocene mollusks were found and at both the deposits 

 rested directly on Miocene beds, so this horizon of fossiliferous sands is probably 

 older Pliocene. The formation contains Macoma lyelli Dall at Gay Head and 

 Area limula on Long Island. Gratacap J describes the discovery of Area (Scaph- 

 arca) transversa Say, and Area limula Conrad, in a "light yellow sandy marl," 

 at a depth of 8 to 10 feet below the surface on the side of a bare hill in a road 

 6 miles east of Southampton, Long Island. Neither of these species is mentioned 

 in the Maryland report on the Miocene (1904). Dall 2 states that Area limula 

 is confined to the Miocene in South Carolina, North Carolina, Maryland, and 

 New Jersey, to the Pliocene in South Carolina, Georgia and Florida, that it is 

 now extinct, and that it was probably the ancestor of Area ponderosa. Gratacap 

 refers the deposit on Long Island to the Pliocene. 



The shell-bearing beds on Nantucket, known as the Sankaty sand in part, 

 were referred by Dall to a late Pliocene age. In this report the Sankaty sand is 

 referred to the Pleistocene, as it was by Fuller. There is an unquestioned older 

 Pliocene horizon on the islands, known only in a fragmentary way, but probably 

 having a considerable extension as a bed of sand, with or without fossils, beyond 

 the two localities at which fossils have been discovered. The bed at Southampton, 

 though not the first discovered nor the most richly fossiliferous, is the only known 

 deposit that presents the possibility of yielding greater results on further ex- 

 ploration. 



The older Pliocene in the cliffs at Gay Head, here correlated with the Tertiary 

 beds of sand found at Southampton, was discovered in a small pocket that had 

 been faulted down into the Miocene greensand bed. The deposit of sand was 

 almost entirely removed in 1889. According to Dall 3 the fauna comprised the 

 following species : 



Venericardia borealis Conrad 

 Astarte castanea Say 

 Spisula polynyma Stm. 

 Corbicula densata Conrad 



Macoma lyelli Dall? 

 Nucula shaleri Dall. var.? 

 Purpura lapillus L. 



1 Gratacap, L. R., Tertiary fossils on Long Island, The Nautilus, 28, pp. 85-86, 1914. 



2 Contributions to the Tertiary Fauna of Florida, 1898. 



3 Dall, W. H., Notes on the Miocene and Pliocene of Gay Head, Am. Jour. Sci., 48, pp. 296-301, 1894. 



