236 T. C. Br otoii — Fauna from Chappaquiddick Island. 



Genus ? sp. ? PL VIII, fig. 9. 



Shell small, loosely coiled, apex acute, whorls five or six, 

 well rounded, rapidly increasing in size, smooth without any 

 ornamentation : suture quite deep and distinct, character of 

 aperture and lips unknown. 



This species is very similar to a Limnaea in shape but can 

 hardly be one of these as it appears to be a salt water form. 



Represented in the collection by a small but very perfect 

 external mold of which a wax impression was taken. 



Ostrea sp. ? 



Several small internal molds of representatives of this genus 

 are present among the fragments of the concretion. These are 

 not sufficiently well outlined to be specifically determined. 

 They seem to represent at least two or three different species 

 and all are comparatively very small. 



Cardium? sp. ? 



Several casts doubtfully referred to this genus are to be 

 found among the fragments of concretion collected by Dr. 

 Hollick. 



These fossils represent a new and distinct fauna markedly 

 different from that of any other Eocene deposits of this 

 country. Since this fauna does not contain a single species in 

 common with the Eocene faunas of the Atlantic slope and 

 gulf deposits, it cannot be accurately correlated with these 

 beds and assigned its proper place in the geologic scale. 

 Nevertheless from the general characteristics of the contained 

 species and their affinities to forms from widely distant prov- 

 inces, the horizon of these deposits can be ascertained with 

 some approximation to the truth. 



Considering the marine Eocene deposits of this country as a 

 whole, we find that they naturally fall into several provinces 

 lithologically quite distinct, and containing faunas with very 

 few species in common. In New Jersey there is a small and 

 isolated area known as the Shark River beds from their out- 

 crop along that river. According to Clark, these beds repre- 

 sent lower Eocene and rest conformably upon the Cretacic 

 below. By early writers they were considered a part of the 

 Cretacic, as there was no marked line of separation between 

 them and the underlying strata. The fossils, however, were 

 found to be of undoubted Eocene character, and although the 

 fauna was lacking in some of the most widely distributed 

 Eocene species, it still contained no characteristic Cretacic 

 forms. 



These Shark River deposits were thought by Harris to rep- 

 resent a higher horizon than the Eocene deposits of Maryland 



