DISTRIBUTION OF FOSSIL ZOOPHYTES. 275 
depths. But in regions where the sea was shallow, during 
the deposition of the cretaceous rocks, beds of coral lime- 
stone were produced; and these also contain littoral (sea- 
shore) shells, associated with the usual sponges and zoophytes 
(Wond. p. 613). 
In the marine secondary formations antecedent to the cre- 
taceous, namely, the Lias and Oolite, coral-reefs, which appear 
to have undergone no change save that of elevation from the 
bottom of the sea, and the consolidation of their materials 
by mineral infiltrations, demonstrate a condition of the ocean 
in our latitudes, which is now only met with in the tropics 
(Wond. p. 614). 
The limestones of the Carboniferous, Devonian, and Silu- 
rian formations, abound in anthozoan corals, and among 
them are many kinds of Cyathophyllum, Lithododendra, Sy- 
ringopora, Catenipora, Graptolites, &c., which are charac- 
teristic of these deposits. 
The Silurian zoophytes are figured in Sil. Syst.; and the 
splendid works on the British Palzeozoic Fossils, by Prof. 
Sedgwick and Prof. McCoy, now in course of publication, 
contain many admirable figures of new, or but imperfectly 
_ known species. 
_ The extensive beds of coralline limestones, which are found 
in the Silurian strata, wherever they occur,—for the lime- 
stones of this system in North America are characterized by 
the same species of corals as those of England,—seem to in- 
dicate that a more equal temperature prevailed throughout 
_ the ocean, at that geological epoch, than at the present time, 
when the geographical distribution of the coral zoophytes is 
strictly limited by temperature. The reef-forming genera 
are now confined to waters where the temperature is not 
below 70°; their most prolific development being 76°. The 
apparent exception, the occurrence of coral-reefs at the Ber- 
mudas, is found to depend upon proximity to the Gulf Stream 
(Wond. p. 614), which brings down the thermal waters of 
