If 
cragin.] DESCRIPTIONS OF SPECTES. 47. 
Occurrence. — As yet known only from the Malone Hills, H miles 
east of Malone station, and only moderately common in the lower 
part of the Theta beds of that locality, occuring with several of the 
smaller species of Gastropoda. Gryphcea mexicana, which ranges 
much higher, is also one of its commoner associated fossils. Twenty- 
three imperfect specimens and fragments were collected. 
GERVILLIA CINDERELLA Sp. 11. 
PL V, fig. 1. 
Shell snbeqnivalve, moderately inflated, somewhat flattened on the 
flank, falciform, the basal region being much produced posteriorly, 
its terminal part tapering; basal margin long, straight, convex- 
posterior border concave; flank-region limited supero-posteriorly 
and in part anteriorly by an abruptly rounded shoulder, the sur- 
face being drawn steeply in to the base of the wing; posterior shoulder 
continuous from the beak to the upper part of the posteriorly pro- 
duced basal region, its axis gently curved with concavity looking 
upward and backward; anterior wing inflated above, concave and 
more distinct from the body of the valve below; posterior wing- 
large, falcate (?) (largely broken off in the type), surface bearing 
delicate concentric growth lines. 
Measurements. — Height, :V2 (plus several) mm.; length, about 
(probably a little more than) 57 mm.; breadth, 15) mm. 
Occurrence. — One specimen, wanting the cardinal region, was 
found by Doctor Stanton in the horizon of the broader phase of 
Exogyra potosina ai the west base of Malone Mountain, a short 
distance north of the southern end. 
GERVILLIA ? RIOGRANDENSIS Sp. 11. 
PI. V. figs. 2, 3. 
Another species of lamellibranch, here provisionally referred to 
Gervillia, was found at the west base of Malone Mountain, associated 
with G. eindercUa. It is represented by a cast, of which considerable 
of the upper posterior region has been removed by weathering, and 
which bears fragments of the shell of the left valve. The form is less 
elongate and more compressed than that of G. Cinderella; the anterior 
border is concave, the ventral border slightly so, the adjoining lower 
part of the flanks being slightly hollow, owing to the strong compres- 
sion of the ventral region. As compared with G. Cinderella, the 
antero- ventral border is more prominent and regularly rounded. The 
shoulder separating the flank from the posterior wing appears, from 
the cast of part of it, to have been much more gently molded, and this 
wing seems to have had much greater development in its lower part; 
surface, as impressed on the mold of a shell fragment, marked with 
