2G0 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



latitudinal differences are considered, are striking. 1 In Colombia such 

 forms as Gryphaea vesicularis, several species of Ammonites figured by 

 Karsten, and the Foraminifera, show a resemblance to the Lower and 

 Middle Cretaceous of Texas, while the Ammonites described by Hyatt 

 from Sergipe were referred by him to genera and species occurring abun- 

 dantly in the Cretaceous of Texas, but unknown to the Californian 

 fauna. 



The Antillean Cretaceous cannot here be discussed, for it has not as 

 yet been sufficiently studied, but will be defined in our forthcoming 

 studies on the island of Jamaica. This is characterized, like the Tertiary 

 formations, by certain variations of fauna due to the environment and 

 the absence of continental sediments in the waters which these species 

 inhabited. 



The Cretaceous faunas of Jamaica, which have been studied in the 

 past by others and which I have personally investigated, while specifi- 

 cally different from those of the United States, apparently do not con- 

 tain a single species which has been found on the Pacific coast. The 

 same may be said of the Cretaceous of Santo Domingo, Cuba, and Trin- 

 idad, which localities include all we know of the West Indian Cretaceous. 



In the States of Guatemala and Chiapas, Sapper has demonstrated 

 and mapped the occurrence of the Cretaceous formations, apparently of 

 Atlantic facies, possessing the peculiar genus Barrettia, which has hith- 

 erto been found only in Jamaica. 



In the vast stretch of Isthmian country lying between Guatemala and 

 the Venezuelan coast, no outcrop of the Cretaceous has been reported 

 except the one near San Jose, Costa Rica, described in this report. 



D'Orbigny's conclusions that the oceans were united across the Isthmus 

 in Cretaceous times were based upon his identification of five of the 

 Cretaceous fossils from the western side of South America with five in 

 the Paris Chalk. The l-emarkable differences between the synchronous 

 Lower and Middle Cretaceous faunas of the California and Texan region 

 on the one hand, and the Andean and Venezuelan-Brazilian provinces 

 on the other, are so great that in our opinion the only interpretation 

 that can be placed upon them, notwithstanding the absence of good 

 fossiliferous Cretaceous localities in Central America, is that the waters 



1 Since this paper was written an excellent resume' of the Cretaceous faunas of 

 Peru, Venezuela, and Colombia has been printed from the pen of Dr. Gustav 

 Steinman, entitled " Beitrage zur Geologie und Paleontologie von Sudameriea," 

 Stuttgart, 1897. It revises the determinations of Karsten, Stellner, and others, and 

 presents comparisons and conclusions which the reader should consult. 



