A VICULA. 
CONCHIPEBA. 
159 
6 . Limsa semisulcata. —The Half-Furrowed Lima, pi. 
LXVII. figs. 13, 14. 
L. semisulcata . Sowerby, Geo. Trans. 2 d Series, IV. 
pi. 11 , fig. 10 . 
Playiostoma semisulcatum• Nilsson, Petrif. Suec. XXV. 
pi. 11, fig. 3. 
Oblong-ovate, very convex, auricles small, nearly equal; 
beaks incurved and short; disk with a series of twelve to six¬ 
teen radiated rounded ribs, extending from the beaks to the 
base ; where the liues of growth cross these, they assume the 
form of short granular scales ; sides smooth. 
The Lower Greensand, Ilythe, Blackdown, and Pul- 
boro ugh. 
7. Lima exjlis. —The Small Lima. 
L. exilis. Wood, Mag. Nat. Hist. 1839, p. 234, pi. 3, fig. 1. 
Inequilateral, oblique, slender, gaping at the sides; some¬ 
what inflated ; hinge-lino a little oblique, and sloping slightly 
on both sides of the beaks, which are distant; ligamentai 
area large, with a rectangular central pit; lunulo smooth 
surface with numerous, fine, radiating, irregular ribs, which 
project a little over the margins; the interstices with many 
very fine concentric stria); length and breadth about an inch 
and a half. 
The Coralline Hag, Ramshot, and the Red Crag, AValton, 
Essex. 
8. Lima oblong a. —The Oblong Lima. 
L, oblonga . Wood, Mag. Nat. Hist. 1839, p. 234, pi. 3 , 
fig. 2 . 
Inequilateral, oblique, sub-compressed, gaping at both 
sides; hinge-lino oblique, sloping on both sides of the beaks, 
which are prominent and distant; ligamentai area broad, with 
a pretty large rectangular pit; auricles with a notch below 
each; surface with many slightly waved, longitudinal, diver¬ 
gent ribs, projecting a little beyond the margins; length 
one inch, breadth six-tenths. 
The Coralline Crag, Ramshot. 
9. Lima fragilis. —The Fragile Lima. 
L. fragilis , Wood, Mag. Nat. Hist. 1839, p. 253, pi. 3 , 
fig. 3. Browns Rec. Couch. Brit. p.J4,pl. 23, figs. G, 7 , 7.* 
Inequilateral, sub-ovate, very convex, fragile ; one side 
straight, the other arcuated; hinge-line oblique; ligamentai 
area broad, witji a largo sub-triangular pit for the reception 
of the cartilage ; auricles small, imperfectly defined ; beaks 
prominent; whole surface with numerous, slightly undulating, 
longitudinal stria), with two or three exceedingly minute in¬ 
termediate ones; length three-fourths of an inch, breadth about 
one-half inch. 
The Coralline Crag, Sutton, and the Red Crag, Walton, 
Essex. 
10 . Lima plicatula. —The Plicated Lima, pi. LXI.* f. 33 . 
L. plicatula . Wood, Mag. Nat. Hist. 1839, p. 235. 
Convex, inequilateral, obliquely ovate, orbicular; anterior 
side truncated ; posterior side much produced ; beaks project¬ 
ing f hinge-lino a littlo oblique ; ligamonal area small; lunulo 
transversely crcnulated; surface with fourteen or sixteen 
rather strong, divergent punctated ribs, which project beyond 
tho margin; the intervening furrows slightly striated concen¬ 
trically ; length two-tenths of an inch. 
The Coralline Crag, Sutton. 
Sub-Genus. —LIMATULA.— S. Wood. 
Shell longitudinal, equivalve, equilateral; sub-auriculated ; 
umbones rather large and prominent; ligamentai area broad, 
with a triangular pit for the reception of the cartilage; sides 
of the valves close. 
1. Limatula ovata. —The Ovate Limatula, pi. LXI.* 
fig. 35. 
L. ovata. Wood, Mag. Nat. Hist. 1839, p. 235, pi. 3, f. 5. 
Equilateral, oblong-ovate, convex; ligamentary area large, 
with a sub-triangular cartilage pit ; binge-lino nearly 
straight; beaks projecting; surface with from six to eight 
rounded, divergent ribs occupying the centre of the disk, 
emanating from tho beaks, and terminating on the basal 
margin, beyond which they project; sides bulging consider¬ 
ably in the centre; length throe-tenths of an inch, breadth 
two-tenths. 
The Coralline Crag, Sutton. 
2 . Limatula sub-auriculata. —The Sub-auricled Lima¬ 
tula, pi. LXI.* fig. 34. 
L. sub-auriculata. Wood, Mag. Nat. Hist. 1839, p. 23G, 
pi. 3, fig. G. Lima sub-auriculata . Brown, Rec. Couch. Brit, 
p. ^ pi. 23, fig. 45. 
Equilateral, oblong-ovate, convex; hinge-line sloping on 
both sides of the beaks; surface w ith many longitudinal di¬ 
vergent strim, tho two central ones opaque, larger, and moro 
conspicuous than the others, and visible internally; the basal 
margin finely crcnulated; length half an inch, breadth one- 
fourth. 
Tho Coralline Crag, Sutton and Ramshot. 
Grand Division III. 
Shells with an elongated marginal ligament. 
Tribe I.—MALLACEA. 
Shells foliaceous, more or less imequivalve, with the liga¬ 
ment marginal, partly linear, and either simple or interrupted 
by crenulations. 
Genus XXI V .—A VICULA.— Lamarck. 
Inequilateral, inequivalve, foliaceous, sub-quadrate, and ob¬ 
lique; binge rectilinear, and produced on each side into 
straight auriform appendages, with a small indistinct tooth 
in both valves; an elongated, marginal, ligamentiferous area, 
widened near its centre ; inside pearlaceous, with one sub¬ 
central muscular impression, and a series of smaller ones in a 
line towards the umbo. 
1 . Avicula papyracea. —Tho Papyraceous Avicula, pi. 
LXI.'"* fig. 11. 1 
Pecten papyraccns . Sowerby, IV. p. 75 , pi. 354 . 
Obliquely sub-ovate, much compressed; valves ncarlv equal 
and flat ; ears large, unequal, rectangular, with broad, diver- 
gent stria), and rather close, longitudinal stria) on the larger 
ear; surface with numerous elevated stria), which are crossed 
by rather distant lines of growth. 
This is not Avicula papyracea of Gold fuss, which I have in 
plate LXI/ fig. LI, and named A. tenuissima , nor is it A. 
papyracea of J. I). C. Sowerby, Geo. Trans. 2d Ser. V. p. 
13G, pi. 8, fig, 16, as I consider that a Posidonomya, and have 
named it papyracea , seo pi. LXI.** fig. 23. 
