2 The American Geologist. July, isw 
The burrows form boldly sweeping, tortuous curves which 
lie in a slightly warped surface and occasionally cross them- 
selves in a sigmoid or "figure 8" path. The transverse section 
of the east is lenticular, averaging ahout 1<> and <> mm. in ma- 
jor and minor diameters. 
PLICATULA SENESCENS. sp. nov. 
Plate I. figs. 17 and 18. 
Shell quite small, compressed, inequivalve, obliquely sub- 
pyriform or inequilaterally rounded-triangular: beaks de- 
pressed and indistinct, that of the right valve sub truncate by 
the scar of adnation ; valves ornamented with numerous 
punctations and short, radially disposed, punctiform wrinkles, 
so arranged that the intervening elevations do not constitute 
distinct, continuous, radial, rib-like plicules such as are seen 
in most species of this genus, but, rather, faintly suggest 
them; margins of valves thickened, that of the left valve 
forming a broad, distinctly elevated, concentrically laminated 
border in marked contrast with the discal sculpture; right 
valve moderately convex, the left flatfish or slightly concave. 
Measurements. — Hight 11; length 10; breadth 4.5 mm. 
Occurrence. — In No. 3 of the Bel videre section, southwest <>t' the rail- 
way station. I have seen but two or three specimens. 
AVICULA BELVIDERENSIS. sp. nov. 
Shell strongly inequivalve, smooth, obliquely purse-shaped, 
larger than that of A. subgibbosa M. & H., as figured in Meek's 
Cretaceous Invertebrata (Plate 28, fig. 12), to which it bears 
considerable general resemblance, differing from it apparently 
in having a longer hinge-line, a relatively larger and more 
prominent anterior and larger posterior ear; anterior ear ab- 
ruptly compressed, marked off by a distinct but shallow sul- 
cus, and, marked with one or two infero-marginal folds; pos- 
terior ear continuous with the gently concave posterior slope 
of the shell ; left valve strongly and rather narrowly arched 
from front to rear, much more convex than the right, its beak 
also more elevated above the hinge-line than that of the latter 
( ? hinge-line as long as or longer than the shell). 
Occurrence. — I have before me thirteen specimens of this species 
from No. 5 and one from No. 3 of the Belvidere section, taken in the 
south and southwest vicinity of Belvidere. All are imperfect, none 
showing complete outlines or the exact form of the posterior ear; and 
none allowing precise measurements. 
