BAENID&. 59 
little or not at all notcht, except in the midline behind, where there is a slight excavation. 
In the nearly smooth hinder border this genus differs from the species of Baéna. 
Most of the sutures and of the epidermal sulci are obscure; and in most parts of the cara- 
pace the sutures are incapable of determination. The sulci bounding the second, third, and 
fourth vertebral scutes are satisfactorily seen. These scutes were very broad, each about 34 
mm.; while the costal scutes were only about half as wide. The areas occupied by the median 
scutes are conspicuously sculptured. The sculpture, as shown by the third scutal area, con- 
sists of ten or twelve prominent, sharp, uneven ridges, which radiate forward and outward 
from the middle of the hinder border of the area. Evidently a somewhat similar, but less bold, 
sculpture characterized the areas of the costal scutes; but these surfaces have been injured so 
that it can not be described. There is no evidence of the presence of supramarginal scutes. 
On the left side the costal and marginal plates are broken away. The anterior and 
posterior buttresses of the plastron are thus revealed; and it is evident that the anterior one, 
joining the second costal plate, projected inward a considerable distance, as in Baéna, to form 
the anterior boundary of a lateral chamber, whose posterior boundary was formed by the 
hinder buttress joining probably the sixth costal plate. 
When the costal plates broke away, the extremities of the third, fourth, and fifth ribs were 
left adhering in the matrix. These evidently past downward deeply against the inner sides of 
the corresponding marginal plates, as in Chelydra. Such was probably not the condition in 
Baéna. The ends of the ribs are terete, not flat as in most other cases. So far as can be deter- 
mined, there were no fontanels between the costal plates and the marginals. 
Of the plastron (plate 7, fig. 5) all is present except the epiplastrals, and possibly the 
anterior part of the entoplastron. ‘The plastron resembles closely that of Baéna; but the hinder 
lobe is not notcht posteriorly, but rounded. There is a considerable fontanel between the inner 
ends of the mesoplastra. This may be due to the immaturity of the specimen; but judging 
from the closeness of all the sutures of our specimen, and from the fact that in Baéna the bones 
soon co-ossify, it seems probable that the fontanel would persist till a late period of life. 
The anterior as well as the posterior lobe has a width at the base of 36 mm. The posterior 
has a length of 30 mm., and the anterior was probably about as long. The posterior lobe 
diminishes in width rather rapidly backward. The entoplastron was unusually long and narrow 
in its hinder portion. Nothing can be determined regarding the intergular and gular scutes. 
The mesoplastron is narrowed at the inner end, as in some species of Baéna. Each is 
traverst by the pectoro-abdominal sulcus. 
The bridge is 30 mm. wide, fore and aft. The inframarginal scutes which covered the 
bridge can not be mapt with certainty, but there can be little doubt that they were present and 
much like those of Baéna. 
P. sculpta may be regarded as a form ancestral to the later numerous species of Baéna 
which have been found in Belly River, Upper Laramie, Puerco, Bridger and Uinta beds. Dr. 
Baur regarded Glyptops plicatulus as the forerunner of Baéna (Proc. Acad. Nat. Sci. Phila. 
1891, p. 421); but we now find in the same quarry from which G. plicatulus has been reported 
a form much nearer to Baéna than is Glyptops. It becomes evident that we must go back much 
further to find the common ancestor of Glyptops and Probaéna. 
Platychelys, of the Upper Jurassic of Solothurn, Switzerland, is closely related to Baéna 
and Probaéna, and has been assigned by Lydekker to the Pleurosternide. It differs in having 
a more highly sculptured carapace, supramarginal scutes, and mesoplastrals which do not 
reach to the midline. . 
Genus BAENA Leidy. 
Shell firmly joined to the carapace by sutural union with the lateral peripherals and by 
broad and high axillary and inguinal buttresses. Hinder border of the carapace scallopt, and 
with an extensive excavation over the tail. Nuchal bone in contact with the first neural; no 
preneural; no supramarginal scutes; anterior lobe of plastron not extended in front of the 
carapace. Mesoplastra large, with the outer ends expanded. Posterior plastral lobe slightly 
emarginated. Intergulars, gulars, and inframarginals present. Skull broad, with the temporal 
region extensively rooft, the squamosals in contact with the parietals. Jugal forming a part of 
