96 
with a deep constriction on each side—deepest on rostral side; 
whole surface costate with rounded ribs which are largest on 
the rostrate slope of umbonal swell; inside of shell marked by 
square ribs corresponding to the intervals between the exter¬ 
nal ones. Exterior also with line concentric strim. 
Edmoxdia? ledoides. —Elongate-ovate, ventricose, slightly 
narrowed and appressed posteriorly ; ventral margin distinctly 
but not strongly curved, hinge margin slightly so; beak sub- - 
terminal, little projecting. Casts with a faint fold running 
from beneath the beak to the postero-ventral region. Cardinal 
processes (teeth ?) consisting of one stout and triangular under 
beak of left valve, and two smaller ones in right valve. Each 
valve has also a pair of slender divergent lamellar teeth (per¬ 
haps 44 cartilage supports,”) exterior to the cardinal ones. 
Length 25.4 mm. (1.) ; height 12.19 mm. (.48-). 
Edmondia mactroides. —‘-Hinge structure and r principal 
characters like E. ledoides , but shorter, more ventricose^ 
rounded on ventral side, sometimes sub-angulated along ante¬ 
rior and posterior unbonal slopes—especially in old specimens. 
Anterior and posterior muscular pits rather deep, round-oval, 
near the beak. Commissure deeply indented anteriorly, be¬ 
neath the beaks. Exterior marked only by faint lines of 
growth. Length 14.22 mm. (.56) ; length of anterior end 4.83 
mm. (.19); height 11.17 mm. [.44]; convexity of both valves 
9.65 mm. [.38]. Longest specimen 30.48 mm. [1.2]. 
Murchisonia mucro. —Small, turreted, of 6-8 rounded 
whorls isolated by a deep suture, and marked by a relatively 
broad, raised, bicarinate band along the middle; lip slightly 
effuse anteriorly ; umbilicus small. Height 5.08 mm. [.2] ; di¬ 
ameter of base 2.03 mm. [.08]. 
Pleurotomaria cavummlicata. — Rather large, deeply 
and broadly uinbilicate, depressed conical, nearly twice as 
broad as high ; whorls 5-6, with subcircular section, the later 
ones flattened above, suture impressed; exterior of whorls 
with obliquely transverse lines which, in the umbilical cavity, 
and sometimes on the base, coalesce into strong ridges. In¬ 
terior smooth ; two or three of the apical whorls often regu¬ 
larly septate. Height 23.88 mm. [.9 : 4] ; diameter of last whorl 
38.61 mm. [1.52]. 
Plettrotomaria Emmetexsis. —Higher than broad ; whorls 
6 to 8, all rounded, marked by a faint median, revolving, nar¬ 
row band, and fine, transverse, sigmoid strise. Cast smooth. 
Height 28.45 mm. [1.12] ; diameter of last whorl 22.64 mm. 
[.89]. 
Pleurotomaria parvispira. —Small, depressed; whorls<4 
to 5, rapidly enlarging, biangulated, the flattened upper surface 
at right angles with the flat peripheral, and with the axis of the 
shell. Surface with faint sigmoid transverse’ stride. Height 
