ckagin.] DESCRIPTIONS OF SPECIES. 7 ( J 
first about two-thirds of the distance from the primary angulation to the posterior 
shell-margin, and which at length reaches that margin at rather more than 
two-thirds of the distance from the beaks to the distal extremity of the primary 
angulation; intercarinal area? concave, that included by the secondary carinse 
forming an escutcheon, those included between the primary and the secondary 
carina^ continuous with the posterior flattening of the umbonal summits; 
entire exterior of the shell presenting numerous strong concentric growth 
lines and divided off on the disk into rather broad, subequal, concentric zones 
by narrow, low, and, in part, obsolescent concentric ribs. Valves thick. 
Measurements. — Height, SS mm.; length (approximately), 93 mm.; breadth, 
74 mm. 
VENERID^]. 
Genus TAPES Megerle. 
Tapes? cuneovatus sp. n. 
PI. XIII, fig. 13. 
Shell gently compressed, thin, cuneate- ovate ; the convex-tapered 
posterior side narrowly rounded at the end; anterior side rounded; 
base gently convex; dorsal margin rather abruptly excavated at 
front of beaks; breadth contained about one and a half times in 
height; height about one and a half in length; beaks placed at pos- 
terior limit of anterior third; surface finely concentric striate. 
Measurements. — Height, 17 mm.; length, 24.5 mm.; breadth, 10 
or 12 mm. 
Occurrence. — A mile and a half east of Ma lone station ; represented 
by a right valve complete as to form, but with the larger part of the 
shell removed by weathering, enough, however, remaining to show 
the character of the ornamentation. 
PHOLADOMYID^E. 
Genus PHOLADOMYA Sowerby. 
Pholadomya tosta (Cragin). 
PI. XV, figs. 2, 3. 
Anatina tosta Cragin, 1S93, Fourth Ann. Kept. Geol Survey Texas, pt. 2, 
p. ms. 
Pholadomya tosta Cragin, 1897, Jour. Geol., vol. 5. p. SIT. 
Shell large among its congeners, moderately ventricose, very inequi- 
lateral, oblong, with rounded extremities and long, straight-convex 
to feebly sigmoid base, pointed-ovate in cross section; the anterior 
region short; the posterior region long and somewhat narrowed, its 
cardinal margin feebly concave; beaks low-arched, in contact, placed 
at about a fifth (sometimes less) of the shell length from the anterior 
end; entire shell presenting fine growth lines and irregularly inter- 
valed, coarser, concentric imbrications, which on an anterior small 
