1980 MACFADDEN & WALDROP: FLORIDA NANNIPPUS PHLEGON 3

without careful consideration of phylogenetic interrelationships. Mor-
ris F. Skinner (in Skinner and Hibbard 1972:117), one of the foremost
students of the Equidae, stated that: "The practice of assigning all
small forms of Hipparion-like equids to Nannippus without careful
consideration of other characters clouds the relationship of many of
the dwarf forms and prevents the recognition of true Nannippus."
Also, this practice lessens the temporal value of Nannippus and the
other relatively unrelated small Hipparion-like forms.
 Besides Mt. Blanco and other localities in Texas (see also Strain
1966, Akersten 1972, Dalquest and Donovan 1973, Dalquest 1975,
Schultz 1977), N. phlegon has been reported from Arizona (Gazin 1942,
Johnson, Opdyke, and Lindsay 1975), Kansas (e.g. Hibbard 1941,
1956, 1970), Nebraska (Skinner and Hibbard 1972), and two localities
in Florida (Webb 1974, Robertson 1976). This horse apparently is
restricted to sediments of Blarican (Pliocene) age, which spans a time
interval from about 4.5 to 2 million years ago.
 This report describes Nannippus phlegon from four localities in
Florida and discusses its biostratigraphic significance and
phylogenetic origin.

 ACKNOWLEDGMENTS
 We thank Beryl Taylor and Richard H. Tedford of the American Museum of Natural
 History, Clayton E. Ray of the National Museum of Natural History, and Ernest L.
 Lundelius of the Univerity of Texas at Austin for lending us specimens from their in-
 stitutions. Roy H. Burgess of Venice, Florida, let us study an important specimen in
 his private collection. Walter W. Dalquest of Midwestern State University also helped
 us with our study of Nannippus beckensis. S. David Webb and Jon A. Baskin critically
 reviewed the manuscript. Waldrop would like to acknowledge assistance in the field
 from John Beaudua, C. David Frailey, and Henry Galiano. Work at the Santa Fe River
 sites was supported by National Geographic Society and National Science Foundation
 grants to Webb. The figures were prepared by Nancy Halliday; Rhoda J. Rybak typed
 and copystyled the manuscript.

 ABBREVIATIONS
 The following institutions are referred to in the text: AMNH, Department of
 Vertebrate Paleontology, The American Museum of Natural History, New York; BEG,
 Bureau of Economic Geology, now part of Texas Memorial Museum (TMM) collection,
 University of Texas, Austin; F:AM, Frick:American Mammals, Department of
 Vertebrate Paleontology, The American Museum of Natural History, New York; FGS,
 Florida Geological Survey (formerly at Tallahassee), now part of the Vertebrate Paleon-
 tology Collection, Florida State Museum, University of Florida, Gainesville; MU,
 Midwestern State University, Wichita Falls, Texas; RHB, Private Collection, Roy H.
 Burgess, Venice, Florida; TRO, Timberlane Research Organization, Lake Wales,
 Florida; UF, Vertebrate Paleontology Collection, Florida State Museum, University of
 Florida, Gainesville; USNM, National Museum of Natural History, Smithsonian In-
 stitution, Washington, D.C.