BOTHREMYDID&. 125 
The bones of the plastron (figs. 131, 132) are so fragmentary and contacts between the 
pieces so rare that it is difficult to obtain measurements. The right epiplastron (fig. 131) is 
represented by two fragments. One of these furnishes the symphysis. This is 36 mm. long 
and the bone is 22 mm. thick. The hinder border was in contact with the entoplastron and is 
18 mm. thick. The other fragment furnishes the hinder end of the epiplastron. There is 
missing probably only a few millimeters of bone between the two pieces. The epiplastron, and 
eherefare the whole anterior lobe, was of a different form from what we see in T aphros phys 
strenuus. From the obtuse free border of the epiplastron to the entoplastron was nearly 
7o mm. If the restoration here attempted approaches correctness the entoplastron must have 
been at least 200 mm. wide. 
The hypoplastra at their inner anterior angles are 23 mm. thick. The upper layers of 
the hyoplastra overlapt somewhat the hypoplastra. 
Of the hinder lobe (fig. 132) there are preserved several pieces. The restoration of this 
lobe has been attempted and the recognized pieces of the lobe are represented by the stippled 
areas. On the right side is seen a fragment which extends from near the inguinal notch to the 
hypoxiphiplastral sulcus. The free border is rather obtuse, but becomes less so toward the 
suture. The upper surface rises rapidly about 40 mm. and the thickness becomes 20 mm. On 
the left side is a fragment presenting a portion of the hypoplastron and 110 mm. of the free 
border of the xiphiplastron. The border may be called subacute. Three pieces of the right 
xiphiplastron enable us to make out its characters; two of these form close contact and give us 
the hinder angle and the notch. The other piece bears on its upper surface the eroded elevated 
scar for articulation with the pubis. It appears to have the size and form seen in the species of 
Taphrosphys. Just outside of this surface the bone is 17 mm. thick. 
The othe in the rear of the plastron had a width of about 185 mm. and a depth of about 
80 mm. As the backwardly projecting angle of the xiphiplastron is approacht the bone 
thickens and the free border becomes very obtuse. The thickness just outside the ischiadic 
scar is 18 mm. The latter was elevated and rough, and apparently pear-shaped in outline. 
The anterior end of the epiplastron is ornamented with a close network of grooves, which 
inclose spaces extremely irregular in size and form. On the hinder end of the bone the inclosed 
areas are larger, more elongated, and parallel with the free border of the bone. The sculpture 
of the rear of f the plastron is similar to that just described. It is obscure on the central portions 
of the plastron. The sulci of the plastron are obscure. On the epiplastron there is a gulo- 
humeral sulcus beginning 38 mm. from the epiplastral symphysis and running backward 
and a little outward to the suture with the entoplastron. 
This species is dedicated to Entellus, who, though old and lacking confidence, had endur- 
ance and beat his younger opponent (Virgil’s A’neid, book v). 
Genus NAIADOCHELYS nov. 
An imperfectly known genus of Pleurodira, having the plastral surface smooth, the hinder 
lobe deeply and broadly notcht, and a large elevated ech! articular surface which extends to 
the midline. 
Type: Natadochelys ingravata Hay. 
This genus differs from Taphrosphys i in having the lower surface of the plastron smooth, 
instead of ornamented with longitudinal or anastomosing grooves, and in having a much more 
extensive articular surface for the ischium. At present, only the hinder half of the xiphiplastron 
is known. 
Naiadochelys ingravata sp. nov. 
Fig. 133- 
This species is based on a fragment furnishing about the hinder half of a left xiphiplastron. 
It was collected in the year 1900, by Professor F. W. Putnam, having been brought to him by 
Indians, at Chaco Cany “on, New Mexico. The geological formation whence it was derived is 
uncertain, but it was probably the Laramie, which is well developt in that region. The 
specimen has been transferred from the department of anthropology of the American Museum 
of Natural History to the department of vertebrate paleontology. ‘T he present number of the 
specimen is 6078. The small amount of matrix yet clinging to specimen is a yellow sandstone. 
