440 FOSSIL TURTLES OF NORTH AMERICA. 
are somewhat indefinite. There is no longitudinal ridge along the premaxillary symphysis; 
hence the species is not a Gopherus, as defined by Agassiz under the name Xerobates. The 
outer masticatory ridge is somewhat tootht; the inner ridge is rugose, especially posteriorly. 
The latter nearly meet on the hinder borders of the premaxilla. The distance across the 
pterygoids, where narrowest, is 18 mm. ‘There are distinct ectopterygoid processes. The 
outward border of each pterygoid is continued backward and outward as a sharp ridge to the 
hinder part of the base of the quadrate. From the fore part of this base another sharp ridge 
runs upward and inward mostly on the quadrate. Between the two ridges is found a rather 
deep groove. 
The lower jaw (fig. 582) is complete. The depth varies from 22 mm, at the coronoid 
process to 18 mm. at the symphysis. The masticatory surface is traverst lengthwise by a deep 
groove; this does not join that of the opposite side at the symphysis. The external masti- 
catory ridge is sharp and furnisht with small tooth-like processes. From these processes sharp 
ridges run down on the outside of the jaw. The internal masticatory ridge rises higher than 
the Feaeuiale It is rough and dentated. Anteriorly these inner ridges are directed forward one 
on each side of the symphysis and terminate in a blunt tooth Pe the outer ridges meet the 
symphysis. 
Fics. 581 AND 582.—Testudo orthopygta. Skull of type, with lower jaw. 3. 
581. Side view. 582. Lower jaw, upper view. art, articular; den, dentary; sur, surangular. 
Several of the dimensions of the plastron of this animal, as given by Cope, differ from those 
obtained by the present writer. In the following table Cope’s measurements are given in 
parentheses, when differing from the author’s: 
Millimeters. Millimeters. 
Length of plastron in midline 515 (615) Width of base of anterior lip 132 (125 
Width of plastron at axilla 330 (360) Width at end of anterior lip 70° 
Width at inguinal border. . 290 (310) Length of anterior lip above... 105 (100) 
Distance between posterior apices 100 
Some of these discrepancies may be due to misprints, some perhaps to different methods 
of taking measurements; but others appear to be obvious errors of determination. 
The plastron (plate 78, fig. 1; text-fg. 583) is somewhat upturned at the front; also 
moderately concave in the middle. Its length, given as 515 mm., is on a straight line from the 
tip of the anterior lip to the bottom of ee posterior notch. The apices of Te posterior lobe 
extend about 24 mm. further backward. The width of the plastron across the middle was 
close to 450 mm. The greater portion of the free borders of the plastron is much thickened. 
The figures indicate the form of the anterior lip. The width, 132 mm., is that taken between 
the points where the sulci forming the outer boundaries of the gular scutes cross the free 
border. Superiorly the lip runs backward some distance beyond ‘this. Fig. 584 is a section 
at what is here termed the base; and fg. 585, a‘section 25 mm. behind the end of the lip. 
Fig. 586 is a longitudinal section of the lip in the midline. It shows to what extent the lip 
is excavated posteriorly. 
The borders of the anterior lobe from the front to the axilla are acute. From the border 
the bone thickens for nearly 50 mm., then thins toward the median portion of the plastron. 
