1890.] NATTKAI. SCIIONCKS OK PIIII.A DKI.I'IIIA. 813 



built upon f*hoals or beds of" sediment " lying a little beneath the 

 .surface, ready to serve as the l)asis for the attachment of coral " 

 ("Structure and Di-stribution of Coral Reefs," 1842, p. 58), a class 

 of structures which the opponents of the subsidence theory of reef- 

 formations fail to recognize as being in consonance with the Darwin- 

 ian hypothesis. They are, according to a strict classification, neither 

 encircling, barrier, nor fringing reefs, and as a fourth class might, 

 perhaps, with advantage be grouped as "patch" reefs. They belong 

 to the same category as the Florida reefs and banks, whose forma- 

 tion has been largely api)ealed to as evidence against the Darwinian 

 hypothesis of subsidence. But neither the Florida reefs nor the reefs 

 of Vera Cruz give any evidence either in favor of or against great 

 subsidence, since they are mere shallow-water formations, and, so far 

 as direct evidence goes, they represent only surface deposits. Yet 

 it is by no means either impossible or improbable that some of them 

 are actually placed on subsided areas, while it is all but j)ositive 

 that others have been brought to their present positions through 

 elevation. Certain it is that movements of elevation have taken 

 ])lace in the Floridian region during a very recent geological period, 

 and it is at least probable that movements in a contrary direction 

 w^ere not wanting at about the same, or a somewhat earlier, period, 

 and again later. ^ In the case of the Vera Cruz reefs we have more 



1 I have discus^ed these points in my report on the geology of the peninsula 

 of Florida (" Explorations on the West Coast of Florida and in the Okeechobee 

 Wilderness" — Trans. Wagner Free Institute of Science, Phil., 1887 — pp. 15, 26 

 -33, 64b), ai;d again in my observations on the coral reefs of the Bermudas 

 (" The Bermuda Islands. A Contribution to the Physical History and Zoology 

 of the .Somers Archipelago," 18811 — pp. 61, 73, 227). Alexander Agassiz well 

 recognizes the nature of the ' patch" reefs, and the possibilities of their formation 

 (following Darwin) without the necessity of either elevation or subsidence (" The 

 . Tortugas and Florida Reefs. " Memoirs Amcr. Acad. Arts and Sciences, 

 XI, part. II, 1885, pp. 118-1!>). But I fail to see the evidence in sup- 

 port of the statement that " on the Yucatan, as on the Florida Bank, the conditions 

 favorable for coral reef growth have been produced, not by the uplifting of the 

 continent, but by the gradual rising of the bank itself into suitable depths in con- 

 sequence of the accumulation of animal debris upon it" {^loc. fit); or for the 

 further statement that " there is practically no evidence that the Florida reef, or 

 any part of the southern peninsula of Florida which has been formed by corals, 

 owes its existence to the effect of elevation " (" Three Cruises of the Blake," I, p. 

 (>1, 1888). In my work on the Bermuda Islands, above referred to, I have con- 

 sidered these points, and attempted to show that the actual geological evidence 

 that we possess in the premises tends largely, I might say, almost wholly, to a 

 conclusion opposite to that which was reached by Mr. Agassiz. Prof. Shaler, in a 



