CONCHIFERA. 
Gervillia. 
164 
above, protruding in a lengthened sharp point, and consider¬ 
ably concave on the margin ; surface with six elevated, narrow, 
longitudinal, divergent ribs, extending beyond the margins, 
and acutely pointed; the central, second, and sixth ribs being 
higher than the others, which are intermediate ones; the rib 
next the larger ear is invariably tripartite; the intercostal 
spaces with fine, irregular, longitudinal stria?; crossed towards 
the base with lines of growth ; margins between the ribs con¬ 
vex ; flat valve, with the hinge-line quite straight, the anterior 
auricle corresponding with that of the lower valve; the larger 
one undefined, acute above, and much less concave on the 
margin than that of the other valve; surface with five or six 
longitudinal divergent furrows, corresponding with the ribs in 
the opposite valve, the intermediate spaces with numerous, 
fine, longitudinal sfcrise ; margins plain and quite circular. 
The Lias. Saltford, near Bath. 
Although Mr Stutchbury's figure is scarcely two inches in length, the 
ribs protrude six-eighths of an inch beyond the margins. 
Genus XXV*— PTERINEA.— Goldfuss. 
Shell equivalve, inequilateral, both sides furnished with 
lateral auricles ; the anterior one short; the posterior distinctly 
defined ; hinge area broad and lengthened, its superior margin 
straight, and the surface generally with a series of parallel 
lines; ligament internal ; hinge with several oblique cardinal 
teeth, situate below the beaks, and with one or moro lateral, 
very oblique, remote teeth, sloping considerably downwards 
from the umbones to the anterior side, with one large muscu¬ 
lar impression in each valve. 
The shells of this genus may easily bo mistaken for those of 
Avicula , where the inside of the valves are hidden from view. 
1. Pterinea ventricosa. —The Inflated Pterinea, pi. 
LXI** figs. 16, 17. 
P. ventricosa. Goldfuss, pi. 119, fig. 2. Fhillips, Pal. Fos. 
p. 49. pi. 22, fig. 82. 
Much and obliquely elongated, its length more than double 
its breadth ; ventricose; hinge-line straight and slightly ob¬ 
lique ; auricles unequal, the anterior ones very small and 
acute, the other very large, extending below the centre of the 
side ; beaks obtuse ; hinge with oblique narrow teeth, gradu¬ 
ally lengthening posteriorly, forming a triangular scries, with 
a series of shorter teeth behind them; surface smooth. 
The Devonian Shales, Newton Bushel. 
2. Pterinea radiata. —The Rayed Pterinea, pi. LXI.** 
fig. 22. 
P. radiata. Goldfuss, pi. 119, fig. 7. 
Transversely oblong; surface with a scries of wide-set lon¬ 
gitudinal, rounded, divergent ribs, with one or two intervening 
ones between each, the whole surface crossed by numerous 
waved stria?; margin scolloped. 
The Devonian Shale, Newton Bushel. 
3. Pterinea spinosa. —The Spinous Pterinea. 
P. spinosa. Phillips, Pal. Fos. p. 48, pi. 22, fig. 8. 
Oblique; deeper valve very convex along the middle, as 
well as the anterior, which is small, rounded, and separated 
from the middle by a deep, broad sinus, and depression ; ante¬ 
rior side expanded and flattened ; whole surface with large, 
longitudinal, wide-set, oblique ribs, which are provided with 
imbricated, distant spines, and crossed by fine concentric 
stria?; on the disks the intercostal spaces are flat, longitudi¬ 
nally striated, as also the posterior wing. 
Devonian Shale, Petherwin. 
4. Pterinea Thompson!. —Thompson's Pterinea. 
P. Thompsoni. Portlock, Geo. Rep. p. 431, pi. 25 A, 
fig. 10. 
Much elongated transversely; convex; body of the shell 
oblique; hinge-line quite sharp and horizontal, extending the 
entire length of the valve, terminating on both sides with 
lengthened acute auricles, with a slight contraction under the 
anterior one; the posterior margin sigmoidal; beak not ex¬ 
tending beyond the hinge-line. 
The Carboniferous Limestone, Tyrone, Ireland. 
Figs. 36 and 37 represent Pterinea Iceris , to shew the teeth of another 
division of the genus. 
Genus XXYL—MONOTIS .—Bronn. 
Sub-equivalve, inequilateral sub-orbicular ; compressed ; 
close; anterior auricle small, with a larger continuous one on 
the posterior side; hinge-line straight, thick, and destitute of 
teeth ; beaks depressed and sub-medial, with a canal below 
them in front, inclining in the right valve, and a plait 
within. Muscular impressions unknown. 
L Monotis decussata. — The Decussated Monotis, pi. 
LXI.** figs. 18, 19. 
M. decussata. Goldfuss, pi. 120, fig. 8. 
Sub-orbicular; under valve convex, the other rather flat; 
hinge-lino straight and horizontal; auricles not refined ; umbo 
rounded and blunt; surface with numerous line, divergent 
ribs, thickly beset with imbricated spines, the intercostal spaces 
with fine longitudinal stria?, crossed by numerous flat, broad 
stria?; margins scolloped ; upper valve with a large posterior 
auricle, hollowed on the side, and defined by four radiating 
ribs; the anterior side with a small acute ear, separated be¬ 
low by a notch ; from the umbo emanate numerous undulating, 
divergent, irregularly-set ribs, which occupy the central por¬ 
tion of the valve, leaving a space destitute of ribs on both 
sides ; the intercostal spaces with numerous shallow, concentric 
grooves, which cover the whole surface. Length six-eighths 
of an inch ; breadth somewhat less. 
The Lias, Gloucestershire. 
Fig. 20 repsesents the hinge of Monotis subcostata. 
Genus XXVII.—GERVILLIA.— Defrance. 
Shell oblong, nearly equi valve, greatly inequilateral, and 
oblique ; hinge-line rather long, linear and nearly straight, 
with several irregular, somewhat transverse, small pits, for 
the reception of the ligament; teeth numerous, more or less 
lamellilbrin, interlocking, variable in direction and size, situ¬ 
ate below the dorsal edge ; each valve with one muscular im¬ 
pression. 
I.Gervillta solenoides. —The Solen-shaped Gcrvillia, 
pi. LX IX. fig. 6. 
G. solenoides. .Sowerby, VI. p. 14, pi. 510, figs. 1 , 2, 3, 4. 
Greatly elongated transversely, its width being nearly eight 
