1913.] NATURAL SCIENCES OF PHILADELPHIA, 493 



TWO COLLECTIONS OF PLEISTOCENE FOSSILS FKOM THE ISTHMUS OF 

 PANAMA. 



BY AMOS P. BROWN AND HENRY A, PILSBRY. 



The two collections of fossils treated of in this paper were briefly 

 alluded to in our second paper on the Gatun Formation,^ issued in 

 January of this year. They were collected by Professor W. B. Scott, 



1911, with the assistance of Mr. D. F. Macdonald, geologist of the 

 Isthmian Canal Commission. As noted in our former paper, they 

 came from two localities near the north end of the canal. 



Collection 1. — From the oyster-shell bearing layers in the Black Swamp 

 near Mount Hope {Monkey Hill). — The top of these beds is some four 

 feet above the present sea level and they are encountered in digging 

 for sewers in the town of Colon. They are also known from Toro 

 Point, across the bay from Colon. The material consists largely of 

 coral mud, with corals and coralline fragments and many molluscan 

 remains mixed with more or less silt containing vegetable matter. 

 It was evidently shipped to us just as it came from the excavations, 

 and contained the small species as they were imbedded in the mud of 

 the sea bottom. No volcanic ash was detected in this material. 

 While the species represented are almost all recent, some of them 

 may be extinct, and at any rate have not yet been found in the living 

 state. 



In a paper published in 1912, Dr. DalP has described four of these 

 found in our material. Besides these four described by Dall, we 

 now add three additional new species ; and a number of others were 

 among the specimens in the collection, but not in sufficiently good 

 form for description. We have found some of these described new 

 species in collections of recent shells in the A. N. S. P. collection, 

 and it may be that none of these new species will be found to be 

 really extinct when the molluscan fauna of that part of the Caribbean 

 is fully known. The fauna of these beds (which Professor Scott has 

 named the Mount Hope Formation) numbers in this collection 69 

 named species of Gastropods, with 3 additional species named only 

 as to genus; 45 named species of Pelecypods, with 3 additional species 

 named as to genus; 2 Scaphopods; 6 species of corals and one 

 barnacle. 



1 Fauna of the Gatun Formation, Isthmus of Panama, II. Froc. A. X. S. P., 



1912, pp. .500-519. 



- New Species of Fossil Shells from Panama and Costa Rica, by W. H. Dall, 

 SmUhxonian Misc. Coll., vol. 59, No. 2, 1912. 



