cragin.] DESCRIPTIONS OF SPECIES. 61 
cuneiform, each consisting of a superior, compressed, tuberculiform 
head and an attenuated cariniform process which dwindles to a point 
below, crossing the longer and gentler posterior costal slope, but not 
crossing the fundus of the intercostal valley quite to the base of the 
comparatively abrupt anterior costal face. The costae are moderately 
interspaced, becoming rather widely intervaled when the shell attains 
the adult size. A small flattened tract formed by the con joined 
antero-dorsal margins, is minutely wrinkled transversely to the 
margins, as the earlier ribs, before reaching the margin, become sud- 
denly reduced and changed to minute linear folds, paralleled in 
their intervals by similar folds, of which there are two in each 
interval. 
Measurements. — Height, about 30 mm. ; length, 36 mm. ; breadth, 
21 mm. One specimen, represented by a considerable part of a right 
valve, indicates, with a breadth of about the same or a millimeter less, 
a height and length 2 or 3 mm. greater. Young examples are rela- 
tively shorter, or more elevated, one such example having height 20 
mm.; length, 20 mm.; breadth, 14 nun. 
Occurrence. — One and a half miles east of Malone station. About 
35 specimens are represented, many of them only by fragments. A 
crushed specimen from this locality has the costal and areal orna- 
mentation exceptionally well preserved and shows an almost spinous 
prominence of the denticles. A cast, representing the anterior two- 
thirds of a right valve on which the cost a? are indicated as plain 
undulations, obtained by Doctor Stanton about 1 mile east of Finlay 
station, is supposed to belong to this species, but may represent T. 
prcestriata. 
Triqonia prosedbra presents points of resemblance especially to two 
of the sections of its genus, and does not agree entirely with either. 
It may be regarded as one of the Clavellatae which, both as to form 
and preiireal ornamentation, has assumed the habit of a common 
phase of the Scabra\ In having an ornamented escutcheon it differs 
from the typical Clavellatae, though not from the Pseudoquadratse — 
which are intermediate between Clavellata; and Quadratse. In hav- 
ing the area bounded on each side by a row of tubercles and below by 
a pronounced limiting ridge it resembles the Clavellata?. 
TRIGONIA PRCESTRIATA Sp. 11. 
PI. X, fig. 7. 
Shell small, crescentic-ovate, only moderately inflated ; area strongly 
and closely striated in a direction oblique to its length, bounded below 
by a rather strongly compressed and prominent limiting ridge or 
angulation; preareal ribs about 12 or 11 in number, coarse, remote, 
and strongly elevated, descending divergently and for the most part 
