1 2 PREFACE. 



excellent time markers iind liorizon iiulirators, as they possess a very small 

 stratigraphic range and a rather wide geographic distribntion. Second, 

 from tlie character of the coral fauna, assisted by the lithology, an attempt 

 has been made to determine the bathymetric conditions under wliioh the 

 strata were de})Osited. Third, all obtainable data concerning the structure 

 and de^'elopment of the species and genera are given, and the relationships 

 to other genera and species are often discussed, so that, wlien possible, addi- 

 tional lio'lit might be tlu'own on (picstions of coral morpholog^' and general 

 classification. 



Tlie scope of this paper is wide, and necessarily very many questions 

 are broached that can not now be answered. An attempt has l)een made 

 to avoid much generalization, because generalizing upon insufficient data 

 witliin the last fifteen years hals put the classification of corals (and in some 

 instances their morphology) in a state of great confusion. 



In ]nx studies I have received numerous courtesies from both institu- 

 tions and individuals in the loan of specimens and otherwise. I have had 

 opportunity' to examine collections belonging to the following institutions 

 or individuals: 



1. United States National Museum; Dr. William H. Dall, Curator of 

 Terti;ir\ Invertebrates. 



2. Mr. T. H. Aldrich, of Birmingham, Alabama. 



3. Wagner Free Institute of Science, Philadel})lua, Pennsylvania; 

 C. W. Johnson, curator. 



4. Philadelphia Academv of Natural Sciences, which contains all of 

 Lea's types and many of Conrad's. Many of these specimens were loaned 

 to me upon the request of Messrs. Heilprin, Pilsbr}-, and Stone. 



5. ^luseum of Comparative Zoology of Cambridge, Massachusetts, 

 through the courtesy of Dr. R. T. Jackson. 



6. Boston Societ}^ of Natural History; Prof Alpheus Hyatt, curator. 



7. Louisiana geological survey, through Dr. Otto Lerch, former State 

 geologist. 



8. Johns Hopkins University; Prof W. B. Clark, curator. 



9. American Museum of Natural History of New York; Prof R. P. 

 Whitfield, curator. 



10. The private collection of ^Ir. J. A. Singley, Giddings, Lee County, 

 Texas. 



