MOLLUSK EXPLORATIONS IN THE FLORIDA KEYS 



By PAUL BARTSCH 

 Curator. Division of Mollusks and Cenozoic Invertebrates, U. S. National 



Museum 



During 1931, my explorations were confined to the Florida Keys 

 with the main object of determining the status of my Cerion colonies, 

 brought here from various parts of the Bahamas and the West Indies 

 to determine the effects of changes in environment upon these or- 

 ganisms, as well as the effects of hybridization produced by crossing 

 various members of the genus. These colonies have been established 

 at various times in the interval between 1912 and the present, and, 

 thanks to the joint cooperation of the Smithsonian and Carnegie 

 Institutions, I have had the opportunity of examining them nearly 

 every year since the beginning of this work. 



Arriving at Key West on August 12, I made a collection of Cerion 

 i uca 11 it m there which I felt might possibly be needed in my experi- 

 ments at the Tortugas. I also examined the two colonies planted at the 

 former Fisheries Station, which were found to be merely hanging on. 



On August 13 I joined the Anton Doltnt on her last trip to the 

 Tortugas, where the time between August 14 and 27 was spent in ex- 

 amining Cerion colonies on Loggerhead and Garden keys, and in 

 photographing the bird rookeries on Bird Key. I also exposed 800 

 feet of standard moving picture film undersea, obtaining additional 

 photographs of the coral reef and its associated elements. I also 

 joined the Anton Dohrn on a deep-sea dredging expedition off the 

 Tortugas, where a lot of very interesting material was collected, which 

 has been brought to the National Museum. 



I shall first say a word regarding the bird rookeries, and then re- 

 turn to the Cerion problem. 



In the Annual Report of the Smithsonian Institution for 191 7, I 

 published a short article on " The Bird Rookeries of the Tortugas," 

 in which were described, among other things, the tern colonies of 

 Bird Key. Since that paper was published, a decided change has taken 

 place on Bird Key. All of its tree, bush, and shrub vegetation has 

 been either entirely swept away by hurricanes or by their after effects, 

 leaving little vegetation beyond the few species of ground-covering 

 plants. Even the many coconut palms planted by the Audubon Society 

 have gone under, only one of them remaining this summer. This 

 change of vegetation has produced an interesting effect upon the habits 



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