EOCENE TESTUDINATA. 
49 
but they present such variations in size and sculpture as to render further 
investigation necessary. The degree of inosculation of the ridges evidently 
dilfers much in different parts of the same carapace, but no portion of it 
presents the open honeycomb pattern of \he. P. fractus. The typical .indi¬ 
vidual is, however, represented only by a hyposternal bone, and portions 
of carapace are only provisionally associated with it. This bone is orna¬ 
mented with sharp, raised, narrow ridges, which are straight or vermiculate, 
and which inosculate but little. The broken base of the bridge is particu¬ 
larly stout, and the thickening continues within the inguinal border to the 
postabdominal extremity. The inguinal edge is thinner, and is incurved at 
the postabdominal gomphosis. 
Measurements. 
M. 
Thickness of hyposternal at middle. 0. 007 
Thickness of hyposternal at bridge. 0. 009 
Seven ridges measure. 0.010 
Plastomenus multifoveatus. Cope. 
Plate XXV, fig. 11. 
Plastomenus multifoveatus, Cope, Ann. Eeport U. S. Geol. Surv. Terrs., 1872, p. 619. 
? Plastomenus catenatus, Cope, System. Cat. Vert. Eocene New Mexico, U. S. Geog. 
Survs. W. of 100th M., 1875, p. 35. 
In this species, the pits of the sculpture are smaller on account of the 
increased thickness of the separating ridges. These inosculate more or less, 
according to the portion of the carapace. There are no welts. Thickness 
of a costal bone (type of P. catenatus), 0“.004. 
Portions of this species from Wyoming were originally referred to the 
P. thomasii; but the individual to which they belong has much wider hypo¬ 
sternal bones in the antero-posterior direction, while the hyposternal of 
P. tJmnasii is more like that of a Trionyx. The New Mexican specimen 
presents some differences, but it is uncertain whether they are specific. 
Plastomenus fractus, Cope. 
Plate XXV, figs. 1-219. 
System. Cat. Vert. Eoceue New Mexico, U. S. Geog. Survs. W. of 100th M., 1875, p. 35. 
Five individuals in a fragmentary condition represent this Turtle, and 
present greater uniformity of character than some of the others. The 
4 G R 
