EOCENE TESTUDINATA. 
51 
M. 
Width of a costal bone of a small turtle. 0.020 
Thickness of the same. , . 0,005 
Five pits in... 0. 010 
Width of a costal bone of the thiu form . v.. 0. 025 
Thickness of the same... 0. 005 
Five pits in.. 0. 010 
Plastomenus serialis, Cope. 
Plate XXV, figs. 8-10. 
Costal bones having the sculpture regarded as definitive of this species 
were found in five different localities; but, as the}^ were found isolated, the 
Other portions of the skeleton cannot be satisfactorily determined. 
The species is readily distinguished by the closely-placed, subparallel 
ridges which cross the ribs parallel to the axis of the body, which are sepa¬ 
rated by one or two rows of impressed dots, or small fossrn. In some speci¬ 
mens, the latter are obsolete. 
Measurements, 
M. 
Width of a costal bone, No. 1. 0. 027 
Thickness of the same.... 0.005 
Four and a half cross-ribs in.. 0. 015 
Width of a costal bone. No. 2. 0. 018 
Thickness of the same.. .. 0. 003 
Three and a half cross-ribs in........ 0. (109 
This is the species which I described in the Systematic Catalogue 
of the Vertebrata of the Eocene of New Mexico under the name of 
P, ftJwinasii, a provisional identification not justified by further exami¬ 
nation. 
Plastomenus lachrymalis, Cope. 
Plate XXV, fig. 7. 
Report on Vertebrata of New Mexico, U. S. Geog. Survs. W. of 100th M., 1874, p. 15. 
Costals with finer pits, the welts broken into tubercles posteriorly. 
The largest species of the genus represented in the Eocene of New 
Mexico. The costal bones are rather finely punctate, the posterior as well 
as the anterior. The anterior costal bones are crossed by numerous ridges 
from side to side obliquely; the obliquity increasing posteriorly. On the 
posterior bones, they are broken into vertical bars, separated by consider- 
