CONCHIFERA. 
Umo. 
17b 
Transversely oblong-ovate ; anterior side short, hardly ex¬ 
tending beyond the beaks, which are obtuse ; posterior side 
obliquely rounded, and angulaied below ; surface with fine, 
numerous, radiating stria), crossed by sharp, pretty regular 
lines of growth, producing a reticulated appearance. 
In the Bath Oolite, in various localities : it is very frequently 
found in numbers of four or five individuals, enveloping one 
another, within the Modiola inclusa , in the manner represented 
in fig. 23. 
Order II.—DIMYARIA. 
Shells with two distinct, remote, muscular impressions ; 
which aro widely separated, and inserted towards the lateral 
extremities of the valves. 
Grand Division I. 
Shells irregular, and always inequivalve. 
Tribe I.—CHAMACEA. 
Shell inequivalve, irregular, attached to other bodies ; hinge 
with one or more largo teeth, and provided with two separate 
lateral muscular impressions. 
G enus I.—CIIAMA.— Bruguiere. 
Shell irregular, thick, usually very inequivalve, for the most 
part covered with irregular spines or foliated processes; urn- 
bones distorted, unequal, distant, and involute; that of the 
attached valve salient at the base, and in some instances pro¬ 
jecting considerably beyond it, the other is for the most part 
reflected over upon its valve, appearing as if imbedded in it; 
hinge with one strong, thick, irregular, oblique, striated, and 
generally crenated tooth iu one valve, which fits into an irre¬ 
gular striated groovo in the opposite valve; each valve pro¬ 
vided with two distant, lateral, muscular impressions; line of 
the mantle attachment entiro ; ligament external, subdivided 
at its posterior extremity; ono of the segments decurrent to 
the point of the umbo in each valve. 
1. Ciiama squamosa. —The Scaly Chama, pi. LXXII.* 
figs. 4, 5. 
C. squamosa. Brander, figs. 8G, 87. Sowerby, IY. p. 67, 
pi. 348. 
Sub-globose, or nearly orbicular, attached by the right valve, 
which is somewhat larger than the left; surface with nume¬ 
rous transverse, imbricated, erect lamina, anteriorly produced 
and ad pressed ; posterior portion of the right valve with obso¬ 
lete ribs; left valve rather convex; inner surface smooth. 
1 he London Clay, Barton and Bracklesham Bay, 
Genus II.—CAPRINA.— D'OrLigny. 
Shell irregular, inequivalve, inequilateral, with conical 
divergent apices, more or less unequally prolonged, and in¬ 
curved upon two opposite planes ; hinge and ligament un¬ 
known ; cavity of the valves divided by a partition into two 
conical unequal chambers ; two muscular impressions situated 
within the small cavities, the one before and below, and the 
other above and behind. 
1. Oaprina Lonsdalii. —Lonsdal’s Caprina, pi. LXXII." 
figs. 10, 11. 
Dicer as Lonsdalii . Sowerby, Geo. Tr. 2d Ser. IY. p. 33 
pi. 13, fig. 4. 
Inequivalve, the larger one in the form of an elongated cone, 
somewhat flattened, and curved twice round; the opposite 
valvo with an oblique conical umbo; external surface squa- 
mose. 
The Lower Greensand, near Caine. 
Grand Division II.—LAMELLIPEDES. 
The foot of tho auimal depressed, lamelliform, and not 
posterior. 
Tribe I.—NAYADES. 
Shells inhabiting fresh waters.—Hinge sometimes provided 
with an irregular, simple, or divided tooth, and a longitudinal 
prolonged one; sometimes tootldess; some liavo irregular 
granulated tubercles, extending the whole length of the hinge- 
line; provided with a compound muscular impression; the 
uinbones or beaks frequently decorticated. 
Genus III.—ANODON.— Bruguiere. 
Shell equivalve, inequilateral, and transverse, for the most- 
part very thin ; hinge-lino nearly straight ; destitute of 
cardinal teeth ; tho hinge being glabrous, and provided with 
smooth laminae; truncated, or forming a sinus at the anterior 
end, terminating the apex of tho shell; two lateral, remote, 
muscular impressions, the posterior ono being compound; 
muscular impression of tho mouth entire, and seldom dis¬ 
tinctly marked; ligament linear, external, sunk in a cleft at 
the anterior extremity. 
1. Anodon cygnea. —The Swan Anodon, pi. LXXIV.* 
fig. 7. 
Anodon cygnea. Brown, Land and Fresh-water Conch. 
Brit. p. 101, pi. 13. 
Inequilateral, oval, tumid, somewhat pointed at both ex¬ 
tremities, slightly open at the sides; beaks depressed; surface 
transversely wrinkled and sub-striated. 
In the Pleistocene Fresh-water Formation, Cropthorn; Bac- 
ton, Stutton; Clacton and Grays. 
Genus IY. — UN 10.— Bruguiere. 
Shell generally transverse, equivalve, inequilateral, free; 
sometimes sub-cordate, or sub-orbicular; pearlaceous within: 
generally covered with a dark olivaceous epidermis; umbones 
usually decorticated and prominent; hinge provided with a 
short, irregular, simple, or double compound tooth, which is 
almost always striated ; with tw'o elongated, compressed, late¬ 
ral teeth, tho front one produced, sometimes obsolete; two 
muscular impressions in each valve, the superior one compound, 
or composed of several divisions; ligament external. 
