T. C. Brown — Fauna from Chappaquiddick Island. 229 



Aet. XXYI. — A New Lower Tertiary Fauna from Chappa- 

 quiddick Island, Martha'' s Vineyard ;* by Thomas C. 

 Buown. (With Plate VIII.) 



Chappaquiddick Island lies at the eastern end of Martha's 

 Vineyard and owing to the shifting nature of the sands and 

 varying tidal currents, it is at times connected with that island, 

 but it is for the greater part of the time completely separated 

 from it. Dr. Arthur Hollick has made a very careful study 

 of the structure of this island and collections of the molluscs 

 and plants found fossil upon it.* The fossil plants have been 

 very fully described by him in the Bulletin of the JST ew York 

 Botanical Garden, vol. ii, No. 7. The mollusc material has 

 not been described and its horizon was provisionally set as Cre- 

 tacic by Dr. Hollick because of the similar lithological char- 

 acter of this material with other deposits on Martha's Vineyard 

 containing undoubted Cretacic fossils. 



A careful study of the fossils has shown that this material is 

 not Cretacic but Eocene in age and that it contains a new and 

 peculiar fauna, a fauna which differs considerably from that of 

 the Eocene deposits of the southern Atlantic slope. 



In describing the deposits from which these molluscan 

 remains were obtained Dr. Hollick says : " . . > the Island may 

 be said to be composed of reassorted drift. . . . These hills in 

 general may be described as kame-like, both in appearance and 

 in composition. They are rounded accumulations of sand, 

 gravel and cobble stones, with some bowlders, and were evi- 

 dently formed by water action. In many places the sand and 

 gravel is cemented together by limonite, forming hard lenses 

 and strata, and ferruginous concretions and shaly fragments 

 are abundantly represented." f 



In his geological studies of Martha's Vineyard and surround- 

 ing islands Professor Shaler recognizes these ferruginous con- 

 cretions and concerning them he says : " On the Island of 

 Chappaquiddick and in the region near Edgartown, occasional 

 fragments of a ferruginous sandstone are found which closely 

 resemble in their general character the materials containing 

 the Cretaceous fossils, but as they offer no organic remains I 

 hesitate to consider them of that age." X 



Dr. Hollick considered these concretions as lithologically 

 identical with those containing Cretacic molluscs and plants 

 and set out to make a collection of organic remains that would 



* The investigations on which this paper is based were carried on in the 

 Paleontological Laboratory of Columbia University and the types of these 

 species are in the university collection. 



f Bull. N. Y. Botanical Garden, vol. ii, No. 7, p. 399. 



JN. S. Shaler, 7th Ann. Report U. S. G. S., p. 326. 



