174 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
beds of Costa Rica,’ are of a clastic nature, and intermixed with volcanic 
débris, and contain a little studied fauna of Rudistes quite suggestive of 
the Antillean type. The oldest known formation of Panama is an un- 
fossiliferous andesitic tuff of Pre-Tertiary and probably Cretaceous age. 
No Cretaceous formations interbedded in igneous deposits analogous 
to these are known to exist on the coast of the North American conti- 
nent north of Tehuantepec, although, as has been shown, active vul- 
canism was in progress during the Upper Cretaceous period in the 
vicinity of Austin, Texas, and southwestward. Whether or not this 
was the most northern extent of the voleanie phenomena which were 
especially active throughout the Central America, Isthmian, Antillean, 
Andean, and Venezuelan regions at that time cannot be stated. 
The northern portions of the South American continent — Colombia, 
Venezuela, and the outlying islands of the Venezuelan seaboard — pos 
sess Cretaceous faunas of a South American type, including beds of older 
epochs than those found in Jamaica. Pteroceras, Cerithium, Turritella, 
Trigonia subcrenulata, Arca, Cardium, and Echinus have been reported 
by the official Trinidad Survey? from Cumana, on the mainland neat 
Trinidad. 
Stratified formations of the type of the Richmond beds, composed of 
impure land derived carbonaceous shales and sandstones grading upward 
into calcareous beds representing the initiative of the great Mid-Ter- 
tiary subsidence, also have wide occurrence in the West Indies, although 
but few attempts have been made at differentiating them from the pre 
ceding group with which they are continuous. 
In San Domingo and Haiti, as in Jamaica, this formation undoubt- 
edly has extensive development. It has been clearly described by Gabb; 
but confused with the equivalents of the Bowden beds. It is most 
probable that the uptilted coarse sandstones, conglomerates near Bao 
and Yagui, and the shales into which they grade as described by him, 
are the equivalents. of the Richmond beds. They have a thickne®® 
between 1,200 and 1,500 feet. Tippenhauer’s* description of the 
Eocene conglomerates of Haiti conforms perfectly with the nature 0 
1 Geological History of the Isthmus of Panama and Portions of Costa Ric 
Based upou a Reconnoissance made for Alexander Agassiz, by Robert T. Hill. 
Bull. Mus. Comp. Zoól., Vol. XXVIII. No. 5, 1898, pp. 226, 227. 
2 Report on the Geology of Trinidad, by G. P. Wall and J. G. Sawkins, Londo” 
1860, p. 166. 
9 Op. cit., p. 94. 
* Op. cit., pp. 85, 80. 
