12 SHALLOW-WATER FORAMINIFERA OF TORTUGAS REGION. 



kingdom. A study of intensive collections from a restricted region 

 like the Tortugas shows this, even in its limited area, as will be noted 

 in detail later. When such collections from widely separated local- 

 ities, as Samoa, the Philippines, New Zealand, and Hawaii, are 

 studied, although of one great geographic fauna, the differences are 

 even more marked. If this is still further extended to a study of 

 Tertiary and Cretaceous, and even older deposits, the differences 

 become greater, just as they do in all other groups of organisms. 



DISTRIBUTION OF FORAMINIFERA OF THE 

 TORTUGAS REGION. 



The twenty stations from w^hich bottom samples were studied in 

 the preparation of this paper, together with collections from reef 

 flats and from the eel-grass, give a considerable range of conditions. 

 The bottom differs in depth and general character. It will be seen 

 by a glance at the accompanying table of distribution (table 5) 

 that at station 42, which was in 18 fathoms to the west of the 

 Tortugas group, there are a number of species not found elsewhere. 

 These are probably species from the deeper Gulf region to the west- 

 ward. In shallow water in the reef itself, where the bottom is of 

 coarse material and often disturbed, comparatively few species are 

 found, and most of these with heavy, thick tests. From the 

 "Drewite" bottom, with its quiet conditions, many delicate tests 

 occur, belonging to species not found in such numbers elsewhere in 

 the region. In the moat at Fort Jefferson, where the shallow water 

 often becomes very warm, species are found not common in the 

 deeper, somewhat cooler waters. According to Dr. Mayor, the 

 temperature in the moat on July 23, 1911, rose to 32.8° to 33.3° C. 

 The water in tide pools on the reef w^as as high as 33° to 38° C. At 

 such temperatures many of the animals are killed. 



With this information, it is of interest to note that the only stations 

 at which Rotalia was found are two in the moat at Fort Jefferson on 

 Garden Key and the other in a very shallow lagoon a few inches 

 deep at Long Key nearby, where the water was warm to the hand 

 at low tide in June. By most authors these specimens would ordi- 

 narily be referred without question to Rotalia beccarii (Linnaeus). 

 I have noticed, however, differences from northern material, and in 

 all probability the Tortugas specimens belong to different species. 

 The various species of Rotalia of this group are, however, in such 

 poor shape that a study of specimens from various regions will give 

 interesting results. 



On the banks of dead coral which become exposed at spring 

 tides great masses of attached Foraminifera develop. Of these, the 

 most abundant is Homotrema, which makes an appreciable con- 



