SECTio:Nr VII. 



UNIONID^ FROM THE CLAYS AT FISH HOUSE, CAMDEN COUNTY. 



The species of Unionoid shells described below occur in bluish-black 

 and dove-colored clays a few miles above Camden, N. J., and are probably 

 from near the base of the Cretaceous series of the State. The latest evi- 

 dence obtained places them as probably equivalent to the Lignite clays 

 near the top of the Plastic Clay series, and below the Lower Marls. This 

 makes them the oldest molluscan Mesozoic fossils of the State, except those 

 from the Woodbridge and Earitan Clays described in Section II. The 

 shells appear to have been first discovered by Professor Cope, of Philadel- 

 phia, and were by him called to the attention of Mr. Isaac Lea, who de- 

 scribed ten of the twelve now known species. Subsequently others col- 

 lected numbers of them. Prof J. Carvill Lewis, of Germantown, Pa., has 

 a large collection, the best of which he very kindly loaned me for use 

 in the following descriptions, and he also has placed me under obligations 

 by the trouble he took to obtain for me the use of Mr. Lea's type speci- 

 mens from the collection of the Academy of Natural Sciences of Philadel- 

 phia. Dr. L. N. Britton has also collected a large number for the State sur- 

 vey, from which some of the figured examples were obtained. 



In regard to the geological position of these shells I shall oflPer no 

 opinion, not having visited the beds myself. Professor Cope appeared to 

 consider them as occun-ing in beds actually below the lowest of the Green 

 Marls, and others with whom I have conversed hold the same opinion, 

 while still others consider them as of much later date. Dr. White in "A 

 Review of the Non-marine Fossil Mollusca of North America,'' Third 

 annual report U. S. Geol. Survey, 1883, says they are ** almost cer- 

 tainly of post-Tertiary date." So far as the shells themselves aff^ord 

 evidence this might be said to be very hkely; still they do not aff*ord 

 any positive information on the subject. They present certain differences, 



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