GEOLOGY AND PALEONTOLOGY OP THE CANAL ZOXE. 587 



mado. At present I have not strong evidence, but it is nevertheless 

 my belief that, while the lower part of the formation is of Burdigalian, 

 the upper part is of Helvetian age, as Douville in essence said so 

 long ago as 189S. This would still signify that the Gatun forma- 

 tion is geologically older than the Miocene of the Chesapeake group 

 in Maryland and Virginia and the Marks Head, Duplin, and Choctaw- 

 hatcheo marls of the Carolinas, Georgia, and Florida. 



Deposits of old Miocene (Burdigalian=Alum Bluff) age arc widely 

 distributed around the perimeters of the Gulf of Mexico and the 

 Caribbean Sea. The Gatun formation extends from Panama into 

 Costa Kica on one side and into Colombia on the other. The lists 

 of corals, Bryozoa, and Crustacea already given show the extension 

 into Costa Rica. Pilsbry and Brown * say regarding a collection 

 from near Cartagena, Colombia, that it is from beds "about equiva- 

 lent in ago to the Gatun in the Canal Zone. " They record the fol- 

 lowing species: 



Fossil mollusks from near Cartagena, Colombia. 



Conns protens TJwasg. Polinices mammillaris (Lamarck). 



molis Brown and Pilsbry. Polamidcs avus Pilsbry and Brown. 



imitator Brown and Pilsbry. Turrilellacariagenensis Pilsbry and Brown. 



aemalalor Brown and Pilsbry. lloydsmithi Pilsbry and. Brown. 



gaza Pilsbry and Johnson. subgrundifera Dall. 



Turris carlagenensis Pilsbry and Brown. tornata Guppy. 



Drilla gatunensis Toula. Pctaloconchus domingensis Sowerby. 



Cancellaria dariena Toula. Dcntalium solidissium Pilsbry and Brown. 

 Mitra longa Gabb. carlagenense Pilsbry andBrown. 



Marginclla mediocris Pilsbry and Brown. Pilar (Uysteroconcha) casta Pilsbry and 

 Oliva sayana immorlua Pilsbry and Brown. Brown. 



Strombina cartagenensis Pilsbry and Yoldia pisciformis Pilsbry and Brown. 



Brown. Area consobrina Sowerby. 



lloydsmithi Pilsbry and Brown. Glycymeris tumefactus Pilsbry and Brown. 

 Solenosteira dalli Brown and Pilsbry. trilobicosla Pilsbry and Brown. 



Murex gatunensis Brown and Pilsbry. lloydsmithi Pilsbry and Brown. 



pomum Gmelin. Ostrea sculpturata osculum Pilsbry and 

 Typhis linguiferus Dall. Brown. 



Cassis monilifera Guppy. 



In 1916, Mr. Gcorgo C. Matson was engaged in geologic work in 

 northern Colombia, near Usiacuri, and sent to the United States 

 National Museum collections of fossils for use in comparing with 

 those from the Canal Zono and Costa Rica. Dr. C. W. Cooke, 

 before being detailed to other work, had prepared preliminary lists 

 of the species of mollusks received up to the time he had to under- 

 take other duties. 



1 Pilsbry, II. A., and Brown, A. P., Oliffocene fossils from the neighborhood of Cartagena, Colombia | 

 with notes on some Haitian species, Philadelphia Acad. Nat. Sci. Proc. for 1917, pp. 32-41, pis. 5, 6, 1917. 



