BAENID&. 95 
restricted. On the other hand, the openings for the hind legs were large. It seems probable 
that these turtles were nceiscomed to lying in the water in wait far passing victims and 
leaping on them and seizing them. The hinder limbs were probably large and strong. 
Quere alium, tua quem moyeant miracula, dixit 
Thescelus; utque manu jaculum fatale parabat 
Mittere, in hoc haesit signum de marmore gestu. 
—Ovid, Met., V, 181. 
Thescelus insiliens sp. nov. 
Plates 24, 25. 
The basis of this species is a specimen which was collected for the American Museum of 
Natural History by Mr. Barnum Brown, in 1goo, in the Laramie beds of Wyoming. The 
locality more accurately stated is on Seven Mile Creek, about 5 miles north of the Chey enne 
River, and about 40 miles west of the town of Edgemont, South Dakota. 
The specimen is a very complete one, presenting both the carapace and the plastron. The 
carapace is in some parts, especially at the peripherals over the bridges, considerably fractured. 
Very few parts are, however, missing, and the form and the general structure can be deter- 
mined. Unfortunately, both the bone and the matrix filling ‘hes interior are very friable. 
Traces of the sutures between the costals are present 2 and have been indicated in the figures. 
It has been found impossible to determine the boundaries of the neurals. Faint traces of the 
sutures have lead to the provisional delimitation of the nuchal bone. The first peripherals are 
probably correctly represented. It is believed also that the sutures between the various bones 
of the plastron are correctly determined, where indicated definitely. The form and extent of 
the epiplastra and entoplastron are conjectural, as no traces of the sutures can be made out. 
The form of this turtle is rather remarkable. Seen from above, the shell resembles that of 
Caretta caretta. It is broad, not greatly elevated, with a median frontal excavation for the 
neck, and narrowed behind. ‘The plastron peernbles greatly that of the species of Baéna. 
It extends, however, far beyond the front of the carapace, while it fails equally as much to 
reach the hinder border of the carapace. The bones are thin. 
The length of the carapace (plate 24) in the midline is 397 mm. The first peripherals 
extend 21 mm. in front of the bottom of the anterior excavation; thus the total length is 418 mm. 
The greatest breadth, across the middle, is also 397 mm. The height above the plastron is 
140 mm., but in life it has evidently been somewhat greater. 
From the ends of the axis of greatest width the border of the carapace curves forward to 
the anterior excavation. Passing backward from the axis referred to, the border is at first 
very slightly concave to just behind the inguinal notches; then rather strongly convex for some 
distance: then again rather strongly concave; at length convex to the midline behind. The 
last concavity in ‘the border would be over the hind legs, when extended backward. Beyond 
the sinuosities mentioned, there are no notches, scallops, nor indentations in the free borders of 
the carapace. The edge of the shell just behind the inguinal notches appears to have been 
somewhat flared upward; but this appearance may be Sie to some distortion. 
In the hinder region of the carapace the peripherals are about 7 mm. thick and with acute 
free borders. As the border of the carapace is followed forward, it becomes more obtuse. The 
nuchal and the first peripherals are about g mm. thick. There are nowhere any carinz or 
bosses on either the carapace or the plastron. 
The whole surface of the carapace is covered with a hard, enamel-like layer, like that of 
Compsemys, Glyptops, and Trionyx. The ornamentation consists of raised dots and lines. 
The latter are sometimes straight, sometimes bent, or brancht, or anastomosing. The general 
effect is that of shagreened leather. On each side of the sutures between the costals a band of 
the surface is striated at right angles with the suture. It is from this striation, when present, 
that the position of the sutures can be made out. Near the rear of the carapace there are such 
indications of sutures as to justify the outlining of a suprapygal similar to that of G/yptops 
plic atulus. 
The anterior portion of the carapace is unusually short, the abbreviation being at the 
expense of the first costals, the anterior peripherals, and the nuchal. The form and position 
of the latter are indicated provisionally, but there seems to be sufficient evidence to show that 
