110 FOSSIL TURTLES OF NORTH AMERICA. 
The fore-and-aft width of the first costal is 64 mm. at the proximal end; its greatest width 
was about go mm. Its length is estimated at 120 mm. On the lower side, at the distal end, is a 
deep triangular excavation, 40 mm. long, for the axillary buttress. From it a broad ridge 
ascends to the rib-head of the costal. ie front of the ridge, along its proximal third or more, 
is another ridge, sharper and more prominent, representing the fat rib. 
The fifth costal is 6 mm. thick at its distal end. On the under surface of the distal end is an 
excavation for the inguinal buttress, a groove ascending about 60 mm. above the peripheral 
border and 6 mm. wide. It is deepest at the upper end, becoming very shallow at the lower end. 
The seventh and the eighth costals are modified for close articulation with the ium. On 
the seventh the thickening produced by the rib proper lies near the hinder border of the bone. 
The hinder part of the thickening is excavated somewhat, espe- 
cially near the proximal end of che costal, to form a broad groove 
Vertebral. Length. Width. 
for the ilium. The proximal end of the groove is closed ‘partly 
by the ridge proceeding from the rib-head of the eighth costal and 
; 75 Bo partly by a subcubic bone, which appears to be the tenth rib. 
2 75 77 
‘ ne co This lies in a depression of the eighth costal. The iliac groove 
4 75 86 is 18 mm. wide at its upper end; and here its bounding walls are 
5 ; 110 
most prominent. Behind the ridge limiting the groove posteri- 
orly is another groove, shallower and roughly Sree which 
appears to have lodged a bone, probably the first sacral rib. 
The surface on the carapace is even, but it is sculptured everywhere by a network of 
shallow grooves. On the costals the network is the coarsest, the grooves lying from 2 mm. to 
5 mm. apart and mostly directed parallel 
with the length of the costal. On the 
neurals and peripherals the network is 
much closer. 
The sulci of the carapace are broad 
and shallow. There is no nuchal scute, 
the first marginals joining at the midline a 
distance of 44 mm. The length of the sul- 
cus between the first and the second margi- 
nals is 44 mm.; that between the second 
and the third, 23 mm. The sulcus between 
the eighth and ninth marginals, on the 
eighth peripheral, is 37 mm. long; the next 
one, 31 mm.; the next, 27 mm. 
The vertebral scutes of this species are 
much narrower than those of TJ. leslianus, 
as shown by the table above. 
The sulcus between the fifth vertebral 
and the hindermost marginals falls behind 
the suprapygal. 
The exact length of the plastron (fig. 
102) can not be determined, the connection 
between the epiplastron and the hyoplas- 
trals not being present. The length was, 
type. 4. Known portions represented by however, NOE far from 340 mm. The notch 
stippled areas. in the rear of the plastron was about 30 
mm. deep, so that the length along the 
midline was about 310 mm. ‘The epiplastrals are relatively small, especially when compared 
with those of Hydromedusa. The hinder end of each is broken off, but each was probably 
about 70 mm. long. The width was about 33 mm., while the greatest thickness of the outer 
end is 7mm. The free border*is acute at the midline, becoming subacute distally. Cope 
describes, under the name of mesosternal, a portion of the entoplastron, but this is now lost. 
He did not give the dimensions. He states that the extremities are acute-angled and that 
the bone was even more transverse than it is in 7. molops. 
hic. 102.—Taphrosphys longinuchus. Plastron of 
