cragin.] DESCRIPTIONS OF SPECIES. 85 
Jpecies of Pleuromya and more commonly in Gresslya, the casts, how- 
ver, lacking the pronounced right dorsal groove of the Latter genus. 
Occurrence. — In the horizon of Exogyra potosina, Gervillia cinder- 
i&Ua, etc., at the west base of the southern part of Malone Mountain, 
and in the Theta member of the Malone Hills, H miles east of Malone 
^station. The types are from the former locality. At both places the 
type variety of Pleuromya inconstans as figured by Castillo and 
tiAguilera also occurs, but in the former situation curia is common, 
i while in the latter it is rare. 
This form, so far as is indicated by the known material from the 
Malone Mountain locality, does not intergraduate with Pleuromya 
^.nconstans, and may represent a distinct species; but at the locality 
gtin the Malone Hills some of the forms of the multivariant inconstant*. 
seem to lead up to it, and it is therefore here considered a variety of 
that species. Its general proportions are not unlike those of the 
Callovian species Pleuromya peregrina d'Orb., from which it is dis- 
tinguished by the recurved posterior region, the position of the beaks, 
ho and the less decidedly excavated anterior dorsal margin. 
A Gresslya-like specimen of Pleuromya from the locality east of 
Malone station, whose form resembles somewhat that of (,'. gregaria 
Goldfuss, is provisionally considered as a mechanical deformation of 
this variety, though it may be such of one of the shorter examples of 
'the variety inconstans, or even be specifically distinct. 
ATNTATIlNriD^. 
Genus ANATINA Lamarck. 
An ATI N A OBLIQTJIPLICATA Sp. 11. 
PI. XVI, figs. 7, 8. 
to 
Shell among the smaller species of its genus, relatively compressed, 
inequilaterally elongate-oblong, rounded anteriorly, attenuated back 
of the beaks; the gaping posterior side shorter than the large and 
closed anterior; the shell somewhat pinched or concave on the ven- 
tral part in advance of the beaks (the ventral margin a little tor- 
tuous?) ; beaks small, low, situated near the limit of the anterior 
third; surface of the thin valves ornamented with concentric growth 
lines, and on the anterior region with a series of coarse and prominent, 
oblique undulatory folds which are nearly straight and trend about 
equally upward and forward. The folds are obtuse at summit and 
are separated by subequivalent round-bottomed intervals; the dis- 
tal 5 occupy the valve to a distance of about 1-1 mm. from its antero- 
ventral margin. 
