58 FOSSIL TURTLES OF NORTH AMERICA. 
characters the skull appears to be cryptodiran in structure. The neck must be regarded as 
primitive and intermediate between the Cryptodira and the Pleurodira. No features strictly 
pleurodiran appear. 
The cervical vertebra are described under the species Baéna riparia and Chisternon 
hebraicum. Considering the shortness of the neck, the structure of the vertebra, and the nar- 
rowness of the anterior border of the carapace, it seems probable that these turtles were able to 
find in the shell little protection for their heads. 
The tail was long, resembling that of Chelydra. With two or three of the skeletons there 
have been found some conical bones, the bases of which were buried in the skin. Some of 
these are symmetrical and it appears probable that they were placed in a row on the upper 
midline of the tail, as in Chelydra. Others of these bones are unsymmetrical, and possibly 
formed parts of lateral rows on the tail. If there had been an armor of dermal bones on the 
legs it would probably have been observed in some of the specimens. 
For the shoulder-girdle and the pelvis the reader is referred to succeeding descriptions of 
Baéna and Chisternon. ‘The limbs are of the walking type. 
The following key may be of some use in determining the genera of the family: 
A. No interhumeral scute. 
a. A preneural present. 
bs. No supramarginallscutes: 45 202...0 saan otis os sem Sets ed antes ee rete tee Chisternon 
bb. Supramarginals: presents: 22. <.isee vieic.cis. the ote sialon a sree ies te osate susapererns oe oath oe Boremys 
aa. No preneural so far as known. 
c. Plastron projecting little, if at all, beyond front of carapace. 
d. Skull with¢choanze*welllin*fronts..c..- ees. eee eee eee Baéna 
dd. Skull with choanz between orbits..................2..0.00005 .... Eubaéna 
ddd. Skull unknown. Plastron with median fontanel.................... Probaéna 
cc. Front of plastron projecting in front of the excavated carapace. 
e. The axillary and inguinal buttresses not greatly developt...... Thescelus 
ee. Axillary buttresses rising high on first costals............... .. Charttemys 
aaa. Characters not well known. A UBT RIES present; the vertebral scutes broad; 9 pairs 
ofscostal ssn type 082 Adon. gn sseelege Sanus & ered orsen se Ayes Clie temeens sae ota skas Neurankylus 
AA. Plastron with an interhumeral scute. 
a» Outer surkacerot plastron nl Oseis seer acne apse ee eee tere teen Polythorax 
. Outer surface of plastron with globular cleyationSa.. amet ae OR eerie Naomichel ys 
Genus PROBAENA Hay. 
A genus closely related to Baéna, but with a more deprest carapace, the hinder border of 
which is little or not at all notcht. Vertebral scutes broader than the costal scutes. Plastron 
with its hinder lobe rounded. A fontanel (permanent?) between inner ends of mesoplastra. 
It is not improbable that when the skull and the cervical vertebra of this genus shall be 
discovered, it will prove that it belongs to the Pleurosternide and that the Baénidz had not yet 
diverged from the former family. 
Probaéna sculpta Hay. 
Plate 7, fig. 5. 
Probaéna sculpta, Hay, Ann. Carnegie Museum, 11, 1903, p. 201, plate iii, figs. I, 2. 
The type is a small and somewhat imperfect turtle, represented by about three-fourths of 
the carapace and the greater portion of the plastron. 
It belongs to the Carnegie Museum, Pittsburg, and was collected by Prof. J. B. Hatcher, 
in 1g0f, in the “‘ Marsh quarry” in the lower portion of the Morrison, or Atlantosaurus beds, 
8 miles north of Canyon City, Colorado, The catalog number is 917. 
The length of the carapace is at present 105 mm., very near the original length; the 
width is 70 mm. The shell has apparently been rather flat, but probably somewhat less so in 
life than at present. The greatest distance between the upper and the lower surfaces is now 27 
mm. The borders of the carapace behind the inguinal notches are considerably flared upward, 
but this may be due somewhat to post-mortem distortion. This border appears to have been 
