﻿GEOLOGY AND PALEOISTTOLOGY OF THE CAXAL ZONE. 587 



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

 my behef 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 1898. 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, Duphn, and Choctaw- 

 hatcheo marls of the Carolinas, Georgia, and Florida. 



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

 distributed around the perimeters of the Gulf of Mexico and the 

 Caribbean Sea. The Gatun formation extends from Panam.a into 

 Costa Rica 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 mollushs from near Cartagena, Colombia. 



Conus proteus Hwass. Polinices mammillaris (Lamarck). 



molis Brown and Pilsbry. Polamides nvus Pilsbry and Brown. 



imitator Brown and Pilsbry. Turriltllacartagencnsis Pilsbry and Brown. 



aemulator Brown and Pilsbry. lloydsmithi Pilsbry and Brown. 



ga:a Pilsbry and Johnson. subgrundifcra Dall. 



Turris cartagencnsis Pilsbry and Brown. tornata Guppy. 



Drilla gatunensis Toula. Pctaloconchus domingensis Soworby. 



Cancellaria daricna Toula. Dentalium soUdissium Pilsbry and Brown. 

 Ultra longa Gabb. cartagenense Pilsbry and Brown. 



MargincUa mediocris Pilsbry and Brown. Pilar (Ilystcroconcha) casta Pilsbry and 

 Oliva sayana immortua 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. trilobicostn Pilsbry and Brown. 



ilurcx gatunensis Brown and Pilsbry. lloydsmithi Pilsbry and Brown. 



pomum Gmelin. Ostrca sculpturata osculum Pilsbry and 

 Typhis linguifcrus Dall. Brown. 



Cassis monilifera Guppy. 



In 1916, Mr. George 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 Zone and Costa Rica. Dr. C. W. Cooko, 

 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. 



• Pilsbry, II. A., and Rrown, A. P.. OliROcene fos'sils Trom the neifjhborhood of Cartagena. Colombia 

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



