This species, when adult, was upward of a foot in length, and in the composition of the shell, number of scutes, etc., resembled the living species of the genus.
The Shoulder Girdle has the form characteristic of the Emydidæ, but presents some peculiarities. The scapula is short, not being as long as the coracoid, and is not so straight or cylindrical as is usual in Emys; but is compressed, and somewhat recurved, and tapers towards the upper extremity, which is marked by a smooth rounded facet for the cartilaginous supra-scapula. The precoracoid is long, sub-cylindrical at its origin, but becomes broad and flat distally; at the extremity it is longitudinally striated. The proximal end is flexed forward at an obtuse angle, and is expanded to form the long suture with the scapula and coracoid. It contributes considerably to the glenoid cavity. The coracoid is remarkably long, and after leaving the sutures with the other elements of the girdle, becomes very broad and thin. This is most marked distally. The anterior border is thickened, and the bone is slightly concave on both surfaces.
The three parts of the shoulder girdle are united by distinct bony symphyses; they differ from some of the modern species, in which there is only a ligamentous union between the coracoid and the other parts. It presents a further difference in the long and slender neck which is formed by the flexing of the precoracoid, and in the shallow and subcircular glenoid cavity. The short scapula and long coracoid would indicate a species with a low, broad carapace, as was probably the case in E. wyomingensis, though much difficulty has been experienced in determining this point, owing to the distortion of the specimens.
Measurements.
| M. | |
| Length of neck to point between coracoid and precoracoid | ·0345 |
| Length of coracoid (about) | ·133 |
| Length of precoracoid | ·114 |
| Length of scapula (about) | ·126 |
BAENA, Leidy.
Baena undata, Leidy.
Cont. to Ex. Vert. Fauna, p. 160.
Three nearly perfect shells of different ages, from Dry and Cottonwood Creeks.
TRIONYX, Geoffr.