224 
Kirtley F. Mather 
a strong sinus on each side of the beak, that in front being 
deeper than that behind, anterior ear separated from outline 
of valve below by a deep byssal sinus, ear extended anteriorly 
nearly or quite as far as is the margin of the valve below, out- 
line of ear meeting cardinal margin in an acute angle, pos- 
terior ear much smaller than that in front; beak somewhat 
flattened, elevated above anterior ear more sharply than above 
posterior ear, situated a little behind the middle and directed 
nearly vertically; surface of valve ornamented by about 25 
flne, slightly wavy, radiating costae separated by flat striations 
about twice their width and crossed by flne, close-set, some- 
what irregular lirae, alternate costae dying out at various 
distances above the margin, the others continuing to the beak; 
surface of anterior ear ornamented by similar costae, about 4 
in number, and concentric lirae, both being somewhat stronger 
there than on the surface of the valve, the sinus between the 
ear and umbo being devoid of radiating costae but crossed by 
the concentric lines which are there incurved upward to main- 
tain their parallel position with respect to the outline of the 
shell. Dimensions of the type specimen are: length, 6.7 mm.; 
height, 6.0 mm. ; convexity of valve, about 1.5 mm. ; length of 
hinge-line, about 5.5 mm. 
Remarks, In a general way this species resembles A. coxanus 
and A, germanus but is obviously distinct from them. Its 
valves are thin and fragile and no perfect specimen has been 
• found, the most complete being preserved as an external mold. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). 
Aviculopecten aurisculptus n. sp. 
Plate XV y figure 12. 
Description. Shell below medium size, sub-ovate in outline 
disregarding the ears, length and height sub-equal, hinge-line 
shorter than greatest length of valve which is found at one- 
third the distance from ventral margin to beak; left valve 
moderately convex, the surface sloping abruptly from umbo to 
auriculations and more gently toward the ventral margin which 
meets the anterior margin in a broad curve, byssal sinus shallow 
and broad; anterior ear triangular, well-defined and somewhat 
