INTRODUCTION. 5 



Sombrero Light, and on four different lines normal to the reef between 

 Sombrero Light and Sand Key, and extending from the shore across 

 the different kinds of bottom. 



In 1869 a few easts were obtained on the Cuba coast and near 

 the Salt Key Bank, and lines of soundings and dredgings ran to the 

 westward of Tortugas. and at intervals of about ten miles between these 

 islands and Sand Key, and between Sombrero and Cape Florida.* The 

 localities of the dredgings are indicated on the map by small crosses. 



As an appendix. I have added a preliminary list of the shoal-water 

 and reef corals of Florida ; a fuller account of them will be given 

 by Professor L. Agassiz. 



In the classification used, the system of Milne-Edwards and Haime 

 has been followed generally; some of their subfamilies, however. I have 

 thought proper to elevate to the rank of families and to separate 

 altogether from their former associations. The affinities of the families 

 to each other cannot be expressed by the order of arrangement in 

 which they are placed, as a family or group may form the connecting 

 link between more than two others. The larger groups are still more 

 difficult to limit than the families, and have not heretofore been hap- 

 pily formed ; as an instance. I would mention the association of the 

 Eupsammidae with the Madreporidae, based only on the porous con- 

 dition of the ccenenchyma, whilst the polyps of the two groups are 

 entirely different from each other. 



As long as we are confined to the knowledge of the hard parts of the 

 corals, their classification must remain incomplete. For a full study 

 of the soft parts a long residence on the spot is indispensable, as 

 the investigation requires much time and patience. Much confusion 

 has been introduced by a hasty examination of imperfectly expanded 

 polyps, in which the shape and arrangement of the tentacles, of the 

 mouth and the folds surrounding it. etc. is often exceedingly different 

 from their condition in a well-developed, healthy animal. 



I must express my thanks for aid received, in the shape of specimens 

 for comparison, or the gift of publications not readily accessible, to Pro- 

 fessor P. M. Duncan of King's College, Mr. W. S. Kent of the British 

 Museum. Mr. J. G. Jeffreys of London, Professor A. E. Reuss of Vienna. 

 Professor A. E. Verrill of Yale College, and lastly and principally to 

 Professor Louis Agassiz. the instigator of these researches, the com- 

 panion during part of the cruise of 1869, and the kind and obliging 

 friend and adviser. 



* The succession of the reefs or keys which may be mentioned in the descriptions of the corals 

 are from west to east: Tortugas, Rebecca Channel, Quicksands, Marquesas, Boca Grande, Sand 

 Key, Smiboes. American Shoal, Babia Homla, Sombrero. Collin's Patches, Tennessee Reef, Alli- 

 gator Reef, Conch Reef, French Reef, Carysfort Reef, Pacific Meet. 



