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 recent 
publications, older Tertiary strata are found in numerous mostly small 
bands in middle Guatemala. А 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. 
Тһе 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, Bowditch, and Carson of the Selfridge Expedition. 
Iam personally satisfied that the formations I have described in the 
1 Physical Geography of Guatemala. Peterman's Mitteilungen, 1896. 
