246 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



It is unnecessary to review the occurrence of the Tertiary littoral 

 north of the Isthmus of Tehuantepec, nor can we here extensively re- 

 view the numerous fragmentary observations upon the region between 

 Tehuantepec and Trinidad. The researches of Sapper in Guatemala, 

 Chiapas, and Yucatan, of Gabb in the Costa Rican region, and of Karsten 

 and Sievers in Colombia and Venezuela, are of chief importance, and the 

 essence of their reports is as follows. 



Guatemala, Chiapas, and Yucatan. — According to Sapper's receut 

 publications, 1 older Tertiary strata are found in numerous mostly small 

 bands in middle Guatemala. A list of fossil genera occurring in these 

 beds is given. They are suggestive of Eocene and early Oligocene age. 

 Fossil wood and lignite also occur. 



Sapper has also shown that the Tertiary formations of Guatemala con- 

 tinue into the northern and middle portions of Chiapas, and in the 

 middle portions of Tabasco. 



Until recently the Tertiary formations of Yucatan were supposed to 

 be entirely of this white limestone class, and hence the absolute con- 

 tinuity of the older marginal Eocene and Oligocene littoral was not 

 traceable. 



The studies of Sapper, however, have revealed the most important 

 fact, that interior of and beneath the white limestone of Pliocene (and 

 possibly late Miocene) age of Yucatan, the older Tertiary deposits of the 

 impure littoral character are highly developed, thus supplying the last 

 missing link in the chain of evidence testifying to the further continuity 

 of this older littoral around the perimeter of the Gulf. Thus the 

 discoveries of this patient German explorer have added greatly to the 

 Tertiary sequence of the Yucatan province. 



Thanks to the studies of Gabb in the province of Talamanca, the 

 southeastern division of Costa Rica, along the Atlantic slope between 

 Port Limon and the Chiriqui Lagoon, we are able to demonstrate the 

 continuity of this land derived series of Tertiary sediments as far west of 

 Colon as Port Limon in Costa Rica, and there can be little doubt, as he 

 stated that he believed, that it continued to underlie the common plain 

 of Costa Rica and Nicaragua along the valley of the San Juan, a region 

 however which neither Gabb nor myself has visited. 



The continuation of the Caribbean Tertiary littoral belt eastward from 



Colon to the mouth of the Atrato may be inferred from the observations 



of Messrs. Maack, Bo wd itch, and Carson of the Selfridge Expedition. 



I am personally satisfied that the formations I have described in the 



1 Physical Geography of Guatemala. Peterman's Mitteilungen, 1896. 



