MOLLUSKS 



By Harald a. Rehder, Smithsonian Institution ^ 



The Gulf of Mexico is, chronologically speak- 

 ing, probably the least known body of water 

 adjoining the United States, and the mollusks of 

 its shores are as yet only imperfectly known. 

 This is particularly the case with the area between 

 Cedar Keys on the Florida coast, and Sabine Pass 

 on the Louisiana-Texas border, and with the part 

 of the coast liae stretching between the mouth of 

 the Rio Grande and the vicinity of Veracruz. 



The littoral fauna of the Gulf of Mexico may 

 be divided into two elements that inhabit different 

 geographical areas. There is first the tropical 

 element found on the Florida Keys and north on 

 the Gulf side of Florida to about Tampa Bay, 

 the northwest coast of Cuba, and the Mexican 

 coast from Cabo Catoche on Yucatdn north to 

 the vicinity of Corpus Christi, Texas (and pos- 

 sibly to near Matagorda Bay). This area forms 

 the southern limit of the Gulf of Mexico and is 

 the only part of the Gulf area in which liviag, 

 fringing reef corals are found. Joubin's (1912) 

 representation of coral reefs in Tampa Bay is 

 obviously an error. 



North of this tropical Caribbean area the fauna 

 takes on a more temperate character, showing an 

 obvious relationship with that of the zoogeo- 

 graphical province generally known as the Caro- 

 linian. The physiography of this area is also in 

 general different from that of the more southerly 

 shores. It is a region characterized mainly by 

 sandy beaches either on the mainland or on low 

 coastal or barrier islands that are separated from 

 the mainland by shallow lagoons or bays with 

 passes or inlets between the individual islands. 

 No coral reefs are foimd in this area, although 

 there are submerged coral banks ofip the coast as 

 far north as northern Florida. 



The mollusks of the deeper waters of the Gulf 

 show, mainly, a relationship with the West 



' Published by permission of the Secretary of the Smithsonian Institution 

 • I would like to acknowledge the helpful suggestions received from Prof. 

 T. E. Pulley of the University of Houston. 



Indian fauna but have also some affinities with 

 those of the deeper waters oflF the southern 

 Atlantic coast of the United States. 



PAST WORK DONE IN THIS AREA 



GENERAL 



The first publication that gave a list of the 

 mollusks found along the entire Gulf coast and 

 discussed their geographical ranges was Ball's 

 (1889) catalog, reprinted, with additions, in 

 1903. Ball divided the southeastern coast into 10 

 geographical districts. Three of these districts 

 covered the area included in this report: Florida 

 Keys, from the Keys north to Charlotte Harbor, 

 West Florida, from Charlotte Harbor to the 

 Mississippi Belta, and the deeper waters of the 

 Gulf east of longitude 90°, and Texas, from the 

 Mississippi Belta to the Rio Grande, and the deep 

 waters south to Yucatdn. The broad extent of the 

 Texas district has led to the inclusion, in later 

 lists, of many species as being found in Texas that 

 have not as yet been recorded from the waters of 

 that State. This is true, for instance, of Johnson's 

 (1934) list mentioned later. 



Maury (1920, 1922) pubUshed a catalog of the 

 recent mollusks of the Gulf of Mexico in which 

 were included some Tertiary species. Johnson's 

 (1934) List of the Marine Mollusca of the Atlantic 

 Coast from Labrador to Texas came out post- 

 humously. This check list, though not always, 

 indicates those species found along the shores of 

 the Gulf of Mexico. 



FLORIDA 



The west coast of Florida is better known from a 

 malacological standpoint than any other section of 

 the area under discussion. Numerous catalogs 

 and annotated lists covering this area were pub- 

 hshed in the seventies and eighties: Calkins 

 (1878, 1880), Ball (1884), Simpson (1887, 1889). 

 Melvill (1881) gave a list of the mollusks of Key 



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