104 TESTUDO. 
plates; the third with the second and third; and in the same manner the remaining 
vertebral plates, to the eighth inclusive, articulate each with two pairs of costal 
plates. 
The first costal plate joins the first to the third marginal plate inclusive. 
Plates of the Plastron.—(Pl. XIX. Fig. 3.) In the largest specimen of Zestudo 
Nebrascensis, in which the sternum is best preserved, the entosternal plate is pyri- 
form, and measures one and a half inches long by sixteen lines broad. It encroaches 
for a third of an inch upon the position of the gular scutes, and extends within a 
line of the humeral scutes. In the other specimens, the entosternal plate reaches 
the boundary of the latter. 
In the largest specimen, the episternal plates are one and a half inch long. 
The hyosternal plates are two and a quarter inches long, and in all the specimens 
articulate with the third to the fifth marginal plates inclusive. 
The hyposternal plates, in the smallest specimen, are one and a half inch long, 
in the largest two inches; and they articulate with the postero-inferior angle of the 
fifth marginal plates, and the sixth and seventh of the latter. 
Scutes of the Carapace.—(Pl. XTX. 1.) The vertebral scutes, from the second to 
the fourth inclusive, are hexahedral, and are broader than they are long. The 
second and third are nearly equal in size, and in the smallest specimen measure 
about nineteen lines broad by fifteen long. The fourth vertebral scute is sixteen 
lines broad by fifteen long, and in another specimen, twenty broad by sixteen long, 
and it has the postero-lateral sides more convergent backward than in the pre- 
ceding scutes. 
Scutes of the Plastron—(Pl. XTX. 3.) Upon the sternum, in all the specimens, 
the scutes agree in the details of their arrangement, except that in the smallest the 
anterior margin of the humeral scutes courses along the bottom of the axillary 
notches, but in the others turns forward and outward to the latter. 
The gular scutes, the position of which is preserved in the largest specimen, are 
one inch in length and are angular posteriorly. 
The pectoral scutes are two inches and one line long. 
The humeral scutes internally measure a half an inch in length, but externally 
expand before and behind, and join the axillary and the fourth and fifth marginal 
scutes. In the smallest specimen they reach to the sixth marginal scutes, but in 
the largest one not within several lines. 
The abdominal scutes of the largest specimen are two inches two lines long, but 
are a fourth of an inch less in the smallest one, and in this they join the sixth and 
seventh marginal and the inguinal scutes, and in that several lines of the fifth 
marginal scutes in addition. 
The lines of junction of the scutes of the sternum with those of the carapace 
are nearly parallel on the two sides, and are undulant and intersect the sutural 
connection of the contiguous plates. 
The axillary scute rests upon the hyosternal and third marginal plates between 
the humeral and fourth marginal scutes. 
The inguinal scute is supported upon the hyposternal plate, and in the largest 
