TRIONYCHIDZ. 493 
with the hypoplastra. There are large fontanels in the midline between the bones just men- 
tioned. The hinder of these fontanels is bounded posteriorly by the xiphiplastra. The latter 
bones appear to have met along the midline without intervening fontanel. Where narrowest 
the bridge is 64 mm. wide. 
The whole lower surface of the hyoplastra, hypoplastra, and the xiphiplastra is covered 
with a sculpture like that of the carapace, except that it is finer. 
The cervical vertebra seen in plate g2, fig. 1, is probably the fifth. Its length from the 
front of the prezygapophyses to the hinder end of the postzygapophyses is 64 mm. 
Seven tail vertebra are present in a series 122mm. long but there were others, now missing. 
The most anterior appears to be the first. These vertebre are greatly like those of Platype eltis 
spinifera, but the ridge representing the neural spine is low aad sharp on the front of the 
vertebra. Posteriorly it rises, becomes quite rough, and reaches a width of 5 mm. From the 
highest point it descends to the hinder end of the postzyga- 
pophyses, at the same time becoming broader. The centrum 
of the first caudal has a length of 20 mm. The sacral verte- 
bra are not preserved. 
The left half of the shoulder-girdle is exposed to view. 
It resembles that of other Trionychide. The distal extremity 
of the coracoid is hidden in the matrix. The procoracoid 
process has a length of 80 mm. The humerus is not per- 
ceptibly different from that of P. spinifera. Its length 
from the proximal surface of the head to the distal end 1s 
95 mm. The ratio of the length of the bone to the length 
of the carapace is about the same as in the living species 
referred to above. The radius has a length of 44 mm. 
Neither ulna is exposed its whole length. The bones of 
the wrist and hand are somewhat disturbed, but they 
appear not to have been different from those of living 
members of the family. The first digit is strongly dev elopt 
and ends in a large claw phalanx. T he claw of the second 
digit was not so powerful. 
The left half ‘of the pelvis is represented by only the 
anterior portion of the pubis and the hinder process of the 
ischium. The right half is complete, except that the upper 
; end of the illum is broken off. From side to side the pubes 
Fi. esc apenas beechert. measured 170 mm. The form of this part of the pelvis is 
ae Xz No. 2358 practically that of Platy peltrs spinifera, The posterior pro- 
aaa cess of the ischium is not so flat as in the species just named. 
The femur appears to have been slightly longer relatively to the shell than in P. sprnifera. 
The total length in a straight line is 110 mm. The tibia is 67 mm. long. The foot presents 
nothing distinctive. 
It appears probable that this individual was a male well advanced in age. 
The U.S. National Museum possesses a specimen which appears to belong to 4. beechert. 
This also was collected for Prof. O. C. Marsh in the Laramie deposits of Wyoming. It 
bears the catalog number 2358. 
There is no part of the plastron present. The median and anterior parts of the nuchal are 
wanting; also the distal extremities of the first three costals of the right side; large parts of the 
distal bal es of the costals of the left side; and the free extremities of all the ie, 
The carapace (plate go, fig. 2; text-fig. 647) was high and vaulted. The anterior margin 
is damaged. The posterior margin is furnisht with a wide shallow sinus. The total length 
was close to 325 mm.; the breadth was almost exactly the same; the height, not reckoning 
the plastron, was about 80 mm. 
There is a preneural present, but its anterior end is eroded away. Behind this there are 6 
neurals, the most posterior being small and wedged in between the proximal ends of the costals 
of the sixth pair. The anterior 4 have the usual coffin-shape; the fifth is nearly four-sided; 
the sixth is oval. The table on page 494 gives the dimensions of the preneural and neurals. 
