406 GEOGRAPHIC DISTRIBUTION OF LIFE IN NORTH AMERICA. 
half are Coleoptera), and fifty genera of Coleoptera and Heteroptera 
alone;* hence the total number of genera must be very considerable. 
Among the Mollusea, Dr. William H. Dall informs me that twenty 
species or specific types of Antillean land shells are known to inhabit 
southern Florida, representing thirteen genera or sub-genera not found 
farther north.t 
So far as vegetation is concerned the case is even stronger, there 
being upward of three hundred and fifty genera of plants in Florida 
that do not inhabit Canada; and Prof. Charles 8S. Sargent, in speaking 
of the trees of southern Florida, states: “A group of arborescent 
species of West Indian origin occupies the narrow strip of coast and 
islands of southern Florida. - - - This semitropical forest belt 
reaches Cape Malabar on the east coast and the shores of Tampa Bay 
on the west coast. - - - The species of which it is composed here 
reach the extreme northern limit of their distribution; they are gener- 
ally small, stunted, and of comparatively little value. Certain species 
however attain respectable proportions: the mahogany, the mastic, 
the royal palm, the mangrove, the sea grape, the Jamaica dog-wood, 
the manchineel, and other species here become considerable and impor- 
tant trees.” (Korests of North America, Tenth Census, 1884, p. 6.) 
From what has been said, it appears not only that Wallace’s state- 
ment that ‘“‘ between frigid Canada and sub-tropical Florida there are 
less marked differences in the animal productions than between Florida 
and Cuba” is wholly incorrect, but that there exists in Florida a well- 
marked sub-tropical fauna and flora consisting in the main (except in 
the case of terrestrial mammals and reptiles which could not reach it) 
of genera. and largely of species, identical with those of Cuba. This 
being the case, is it not fair to turn the tables and ask Wallace what 
constitutes the barrier that so effectually holds back hundreds of genera 
and a multitude of species of Antillean or tropical American plants, 
insects, land mollusks, and birds now inhabiting sub-tropical Florida? 
* Mr. Schwarz has kindly given me the following list of families of Central 
American Coleoptera, indicating the number of genera in each family known to 
inhabit semitropical Florida, but not found elsewhere in North America: Carabida, 
2 genera; Phalacridaw, 1; Coccinellide, 1; Cucujide, 1; Mycetophagide 1; Elateride, 
1; Scarabwide, 2; Cerambycide, 5; Chrysomelida, 4; Tenebrionide, 3; Monommida, 1; 
Otiorhynchide, 1; Curculionidae, 6; Brenthide,1 [this is the only genus which reap- 
pears at Cape San Lucas]; Calandride, 3; Scolytidew, 3; Authribide, 2. He informs 
me also that 11 genera of tropical American Heteroptera have been found in the 
same belt. 
+The forms here referred to are: Strobila hubbardii Brown; Helix ceca Helix 
varians Mke.; Bulimulus multilincatus Say; Bulimulus dormant W. G. B.; Orthalicus 
undatus Brug; Liguus fasciatus Miiller; Liguus fasciatus var. Stenogyra gracillima 
Pfr.; Stenogyra subula Pfr.; Macroceramus gossei Pfr.; Macroceramus pontificus Gld. 
(also oceurs in Texas); Strophia incana Binn.; Auricula pellucens Mike. ; Tralia minus- 
cula Dall; Melampus (Detracia) bulloides Mont.; Pedipes mirabilis Muhlf.; Pedipes 
elongatus Dall; Planorbis tumidus Pfr.; Spheriwm cubense Morelet. 
