44 MALONE JURASSIC FORMATION OF TEXAS. [bull. 206. 
prominent anterior ear. Doctor Stanton also obtained a fragment 
from about a mile south-southeast of Finlay station. 
Lima ( ctenostreon ) riograndensis sp. n. 
PL V, fig. 4. 
Shell large and thick, equivalve, somewhat inequilateral, or ob- 
liquely round-oval (the base swung somewhat forward), ventricose, 
.interiorly gaping, radially large-ribbed; ribs broad and loAv-convex, 
about 11 or 12 in number on each valve, separated by flat-concave 
intervals about as broad as themselves; the surface marked with 
sinuous-concentric growth lines and coarse, laminated imbrication! 
which present convexities upward and downward on the ribs and 
intervals respectively, the laminated imbrications in places thickened 
so as to nearly fill the shallow 7 intervals. The ears of the type are 
broken off. The presence of a byssal sinus is indicated by the direc- 
tion of the growth lines on the basal remnant of the anterior ear. 
Measurements. — Height about 125 mm.; length about the same; 
breadth, 80.5 mm. The thickness of the shell varies from about 7 
mm. on the basal slope to about 13 mm. in the dorsal region. 
Occurrence. Only the single type specimen is known. This was 
found on the upper part of the Theta outcrop, 1-| miles east of Malone 
station, associated with specimens of Trigonia vysehetzkii, Astartm 
i;nihmensis, etc. 
The species seems to considerably exceed in size Ct. proboscidea 
Shy., of the Oxford. The only Ctenostreon that has hitherto been 
known from North American rocks is an undescribed species reported 
by Hyatt from the lower Jurassic of Ta^dorsville, Cal. 
PECTHSTIl )JE. 
Genus PECTEN Klein. 
Pecten (camptonectes) insutus sp. n. 
PI. IV, figs. 11, 12. 
Shell pyramidal-subcircular, somewhat inequilateral, with greater 
anterior than posterior extent, inequivalve; left valve having a fair 
degree of convexity; right valve flattish-convex; beaks rather 
pointed, not rounded in well-preserved specimens, the right one but 
slightly inflated; anterior straight or slightly concave and posterior 
usually slightly convex (sometimes in part incipiently concave); 
dorsal margins of body of either valve making a right angle, or often 
considerably less than a right angle, with each other; anterior ear 
large, its hinge, or crest line, about twice as long as that of the poste- 
rior ear, and its anterior margin reaching about three-fourths as far 
