BULLETIN FLORIDA STATE MUSEUM


TABLE 5.-MEASUREMENrTS OF RADII FOR Nannippus phlegon FROM FLORIDA.

 Trans. Trans.
 AP diam. width AP diam. width
 prox. art. prox. art. dist. art. dist. art.
Specimen Length surface surface surface surface*
UF 7260 224.6 22.8 41.3 23.6 38.3
UF 7263 197.7 19.5 34.8 20.7 32.4
*Includes tuberosity for medial ligament and distal articular surface of ulna.

distal articular surface is only slightly concave, which is the condition
in advanced horses (Sondaar 1968).
 The left medial metacarpal, represented by UF 7264 and UF 22619,
is elongate with a relatively narrow shaft (Fig. 9, Table 6). On the prox-
imal articular surface the transverse width is greater than the
anteroposterior diameter, which is the condition in advanced horses
(Sondaar 1968). This proximal surface consists of a large and roughly
triangular facet for the magnum. Lateral to this facet is another facet
for the hamatum. Sondaar (1968) noted that the angle between the
facets for the magnum and hamatum is 1000 inMesohippus, 1200
in Parahippus, and 1600 in Equus. This angle in the two Florida N.
phlegon specimens is approximately 1390 and 1480 (Table 6). On either
side of the volar part of the shaft, distal to the proximal articular sur-
face, are concavities with small facets for the lateral metacarpals II
and IV. The medial metapodial shaft is approximately oval in cross-
section, although the volar surface is somewhat concave. About
halfway down the volar side of the shaft is a nutrient foramen. On
either side of the volar surface roughened elongate areas serve as at-
tachments for the interosseous lateral metacarpal ligaments. These
surfaces become poorly defined distally; they appear to extend at least


TABLE 6.-MEASUREMENTS OF MEDIAL (III) METACARPALS FOR Nannippus phlegon
 FROM FLORIDA.
 UF 7264 UF 22619
 Left Right
Length* 200.6 208.8
AP length prox. surf. 20.1 23.8
Trans. width prox. surf. 27.1 28.8
Angle on prox. surf. schaphoid/hamatumt 139 1480
Width distal prominences 23.1 23.1
Width distal art. surf. 22.5 24.4
Ratio width dist. prom./width dist. art. surf. 1.02 .95
Angle inscribed dist. art. sag. ridget 240 265
*Scaphoid facet on proximal articular surface to sagittal crest on distal articular surface.
tProbably accurate to approximately +15.


Vol. 25, No. 1