52 
EOCENE TESTUDINATA. 
able intervals, and of linear form. The j)Osterior costals reach a thickness 
of 0“.006 and a width of 0"\025. 
The pitting of the posterior part of the carapace distinguishes this 
species from the P. cedemiiis. 
Blit one specimen obtained. 
BAENA, Leidy. 
Baena arenosa, Leidy. 
Plate xxiv, fig. 32. 
Keport U. B. Geol. Surv. Terrs., i, p. 101. 
One specimen obtained, which consists of the middle transverse portion 
of a chelonite, the only one procured by me in New Mexico. It exhibits 
the characters of specimens from the Bridger beds of Wyoming in the 
longitudinal and oblique ridges of the vertebral region and flared postero¬ 
lateral border of the carapace. 
Bleasiirements. 
M. 
Total width. 0. 245 
Depth at middle .. ...... 0.110 
DERMATEMYS, Gray. 
Baptemys, Leidy, Report U. S. Geol. Surv. Terrs., 1873, p. 154. 
Dermatemys costilatus, Cope. 
Plate xxiv, fig. 32. 
System. Cat. Vert. Eoceue New Mexico, U. S. Geog. Survs. W. of 100th M., 1875, p. 36. 
Six individuals contribute fragments to our knowledge of this species, 
but without the completeness desirable. The species is essentially char¬ 
acterized by the presence of an elevated but obtuse rib, which crosses the 
costal bones at right angles to their length. As costals with all degrees of 
definition of the rib are preserved, I suppose that it disappeared at the 
middle of the carapace, or onl}?^ existed on the posterior portion. Associ¬ 
ated with the costals are vei’tebral bones, with a similar, but more pronounced 
rib on the median line; this, also, is faint or ivanting on associated verte- 
brals. I therefore suppose that this keel, also, is confined, as in the 
D. vyomingensis, to the posterior extremity of the carapace. Other portions 
of the skeleton are of uncertain reference; but there are associated, in four 
