DISTRIBUTION OF THE MARINE SHELLS OF FLORIDA.* 
BY DR. WILLIAM STIMPSON. 
OxE of the most striking peculiarities of the zoology of 
Florida is the diversity in the character of the littoral shells 
of the two sides of the peninsula. The naturalist passing 
from St. Augustine to Cedar Keys finds upon the western 
beach a group of shells so different from those he had seen 
upon the Atlantie shore, that he is reminded of the similar 
(though vastly greater) difference in the fauna which exists 
on the two sides of the continent itself; for instance, at the 
isthmus of Panama. This diversity is seen in the common 
large shells as well as in the fauna taken as a whole. Thus 
on the east coast Busycon canaliculatum, B. carica, Dosinia 
discus, Arca incongrua and A. Americana are the most 
abundant shells, while they are not found at all on the west 
coast; and at Cedar Keys and Tampa Bay we find the sub- 
tropical species Cassidulus corona, Busycon perversum, Py- 
rula papyratia, Strombus alatus, Bulla occidentalis, Callista 
gigantea, Dosinia elegans and Arca Floridana? strewed on 
the beaches in great numbers, while they occur but rarely on 
the east coast; some of them not at all. The list presented 
contains the names of three hundred and fourteen species 
collected by me on the two coasts, of which only one hun- 
dred and forty-five, or less than half, were common to both ; 
fifty-eight being peculiar to the east and one hundred and 
eleven to the west coast. Several of these species are in- 
deed representative, but specifically quite distinct. These 
results will no doubt be considerably modified by future re- 
searches, as some of the smaller species may have escaped 
detection on one or the other of the two shores, although 
really existing upon both. But the fact will, nevertheless, 
remain that a marked difference exists between the faune of 
these shores notwithstanding their proximity and notwith- 
* Abstract of a paper read at a recent meeting of the Chicago Academy of Sciences. 
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