202 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
cording to A. Agassiz,! this is mostly of a Pacific type, which has existed 
in the Gulf and Caribbean since at least as far back as Cretaceous time. 
The minority of Atlantic forms from this fauna may also suggest that a 
partial barrier at least then existed to the eastward side of the Carib- 
bean. From Florida to the northeast corner of South America we now 
| have a chain of submerged banks, which constitute the rim of the Gulf 
| and Caribbean basins and which may or may not represent elements of 
this ancient Jura-Cretaceous Isthmus, — the same which has been fre- 
quently used as data for constructing a hypothetical and impossible 
Windward bridge during later epochs. This is still covered by coatings 
of oceanic debris, or capped by volcanic ejecta, which rise at intervals as 
tips of land above it. The configuration of these submerged rims and 
islands is that of an old dissected land. 
The submerged bench off the Floridian coast deflects southeastward 
towards and practically continuous with that of the Bahaman banks, 
where its continuity is broken by great western indentations extending 
along the north side of Eastern Cuba, Haiti, Porto Rico, and the Virgin 
Islands. Thence along the Windward Archipelago to the South American 
coast there are many banks which might be construed as such elements. 
The present outer rim of the American Mediterranean may indicate the 
former continuity of the Isthmian region of Jurassic time. If the Wind- 
ward bridge did not exist at this period, it never existed, — certainly not 
since Eocene time, as will be shown later. 
Hovey has described a series of specimens obtained from a well bored 
to a depth of 2,000 feet at Key West. The Vicksburg formation was 
penetrated completely, the boring passing into the underlying Eocene 
between the depths of 1,450 and 1,875 feet. It is quite probable that 
the former is the base of the Vicksburg. There is indisputable geologic 
evidence in the land-derived material of the Eocene sedimentary rocks 
| of the Antilles, the Virgin Islands, the Caribbees, and Barbados, that land 
| areas from which they were derived existed in this general region in 
Cretaceous time. 
Westward of this hypothetical bridge there could have stood but one 
or possibly two islets in the present Central American region south of 
the southern end of the Mexican Cordilleras. Rising east and west 
H through the States of Oaxaca, Chiapas, and Guatemala, and probably 
| in Cuba and Haiti, there are ancient ridges of Paleozoic sediments and 
igneous rocks, — short erescents curving to the northward and now 
1 Three Cruises of the Blake, Vol. I. p. 167. 
2 Bull. Mus. Comp. Zoól., 1896, Vol. XXVIII. No. 3. 
