404 FOSSIL TURTLES OF NORTH AMERICA. 
the third, which is nearly square, and the fifth, which is rhomboidal. ‘The table gives the great- 
est length and width of each neural. 
The costal plates have undergone considerable differentiation in form. ‘The second, 
fourth, sixth, and eighth have narrow proximal ends and wide distal ends; while the third 
and fifth have wide proximal and narrow distal ends. The 
Neurats (| "Hedeeh. > width. third comes into contact with 3 neurals, the fifth with only 2. 
It is not unlikely, however, that other individuals will present 
variations in the forms of the neurals and costals. 
’ 58 “ The free borders of the plastron (plate 67, fig. 2; text-fg. 510) 
; es Ee are acute. The dimensions of the lobes are given in the table of 
4 35 50 measurements. ‘The anterior lip projects beyond the front of the 
"i Se ve carapace about 50 mm. The base is 87 mm. wide from the 
7 28 46 crossings of the gular sulci over the free border. The length of 
8 28 29 
the lip is 43 mm. The sides converge somewhat, and the rounded 
anterior border is furnisht with 6 blunt teeth. The upper surface 
of the lip is convex, and it rises backward until the thickness becomes 33 mm. The hinder 
face of this thickening is somewhat excavated. The entoplastron is pointed in front, broad 
and somewhat rounded behind. 
The posterior lobe ends behind in 2 broadly rounded apices, which inclose a deep and 
sharp notch. The borders of the apices are tootht. Just behind the inguinal notch the border 
of the hypoplastron forms a wall about 25 mm. high. From the summit of this there is a slope 
to the free edge. 
The sulci of the carapace are narrow grooves with raised edges. The nuchal scute has a 
width of 28 mm. behind, but it is narrower in front. The sulci on the bridges are directed 
downward and forward. The vertebral scutes have considerably 
less lateral extent than do the costals. The accompanying table 
ee aa Bea ig presents in millimeters the greatest length and width of the 
vertebrals. 
: “4 eos The gular scutes encroach on the entoplastron. The humeral 
; 81 8c scutes meet along the midline for 76 mm.; the pectorals, 56 mm.; 
4 75 82 the abdominal, 118 mm.; the femoral, 52 mm.; the anal, 36 mm. 
5 go 135 
Of the other parts of the skeleton there are present the 
humerus, the pelvis, both femora, and the right tibia. The 
humerus (fig. 511) lacks the distal end. It was bent more strongly than that of Gopherus 
polyphemus, and the tuberosities are more strongly developt. athe pelvis 1 is represented by 
hes. 512 and 513. The ischial tuberosities are pointed, and their apices are 45 mm. apart. 
The extremity of the lateral and anterior pubic processes are missing. The ilium has the 
proximal end much broadened antero-posteriorly, it being about 44 mm. The femur (figs. 
514, 515) 1s unusually straight. The digital fossa is rather deep. 
In the Marsh collection at Yale Univ ersity there is a large specimen which 1s to be referred 
to this species. It was collected for Professor Marsh by Mr. ]. B. Hatcher in the year 1889, 
in the Titanotherium beds of South Dakota. It is at present designated by the receipt numbers 
“2054, box 1.’’. The specimen was flattened somewhat during inne but it was probably 
originally of deprest form. Most of the hinder peripherals, are now missing, as is also the 
plastral lip. The second neural of this individual is octagonal, but the aides which are in 
contact with the first and third costals of each side are very short. The third neural is approx- 
imately square. All the others are hexagonal. The two suprapygals are about as in the type. 
The costal plates are strongly modified, having their proximal 
Qoeul Width Width ends alternately narrow and wide, while the distal ends are 
vpperend. Towerend- alternately wide and narrow. Their dimensions are presented 
in the table herewith. 
i ‘6 The first peripheral has an extent, backward from the free 
38 8s edge, of 50 mm. The bridge peripherals rise a distance of 88 
Aun WwW wv 
38 25 mm. above the carina which joins the free border of the third 
, 3 5 peripheral with that of the seventh. On some of the free periph- 
erals there is found a mucro, as in the type specimen. 
