CLASS SECOND. 
CONCHIFERA; OR BIVALVES. 
Animals soft, inarticulate, destitute of a head or organs 
of vision, and always fixed within a bivalve shell; pro¬ 
vided with external branchiae, their circulation is simple, 
and heart unilocular. 
All the species are aquatic, living either in the sea or 
fresh waters. None of the animals have an internal 
shell, the body is invariably soft, and the mouth is situate 
near the left side of the hinge. 
Grand-Division I. 
Ligament none or unknown, or in its stead a tendinous 
chord, which supports the shell. 
ORDER I_MONOMYARIA. 
Animals provided with but one muscle of attachment, 
or adductor muscle, which leaves one subcentral muscu¬ 
lar impression inside of each valve. 
FAMILY I—BRACHIOPODA. 
Shell bivalve, adhering to extraneous marine bodies, 
either by the shell itself being in contact with them, or 
attached by a tendinous chord. Shells not quite equi- 
valve, and open by a hinge. 
Genus I.—LINGULA.— Bruguiere. 
Shell equivalve, equilateral, oblong-ovate, compressed, 
thin; acute and gaping at the umbones; slightly trun¬ 
cated or trilobate at the base; muscular impressions 
situate towards the centre of the valves; external surface 
covered with a glossy, thick epidermis; hinge destitute 
of teeth; shell suspended by a cylindrical, fleshy, tendi¬ 
nous pedicle, attached to the umbones. 
1. Lingula ovalis. —The Oval Lingula, pi. XLIX. fig. 2. 
Lingula ovalis . Sowerby, I. p. 56, pi. 19, fig. 4. Fleming, 
p. 368. 
Oblong-oval, smooth, depressed; beaks rounded and blunt; 
base broad and circular. Length half an inch; breadth a 
quarter. 
London Clay, Pakefield, Suffolk. 
2. Lingula elliptica —The Elliptical Lingula, pi. XLIX. 
fig. 3. 
Lingula elliptica. Phillips, II. p. 221, pi. 11, fig. 15. 
An elongated ellipsis, retrally acuminated; surface plane, with 
wide-set, slender stria?, radiating from the umbones; basal line 
rather acute. 
Mountain Limestone, Ashford, Derbyshire. 
3. Lingula squamiformis— The Scale-shaped Lingula, 
pi. XLIX. fig. 4. 
Lingula squamiformis. Phillips, II. p. 221, pi. 11, fig. 14. 
Oblong; umbones acuminated; base truncated; superior por¬ 
tion of the valves inflated, compressed below; an oblong-oval 
depression in the centre; sides parallel; surface with longitudi¬ 
nal and concentric lines, and with radiating striae at the base. 
4. Lingula Mytilloides —The Mytilus-like Lingula, pi. 
XLIX. fig. 6. 
Lingula Mjjtiloides. Sowerby, I. p. 55, pi. 19, fig. 1, 2. 
Fleming, p. 368. 
Oval, smooth, shining; umbones obtuse; narrower above, and 
well rounded at the base, where it is somewhat flattened. 
Carboniferous Limestone of Durham, &c. 
5. Lingula Beanii —Bean’s Lingula, pi. XLIX. fig. 7. 
Lingula Beanii. Phillips, I. p. 128, pi. 11, fig. 24. 
Oblong-ovate, smooth, glossy; somewhat narrow above, with 
projecting beaks, which are somewhat obtuse at the point; sides 
nearly parallel; base rounded; surface with delicately marked 
lines of growth. 
Blue Wick of the Inferior Oolite. 
6. Lingula pauallela —The Parallel Lingula, pi. XLIX. 
fig. 11 and 15. 
Lingula parallela. Phillips, II. p. 221, pi. 11, fig. 17, 18, 19. 
Ovate, nearly equal at both extremities, front a little more 
rounded than the other end; umbones a little elevated, but not 
projecting beyond the extremity; surface with shallow lines of 
growth. Fig. 11, the flatter valve; fig. 15, the deeper one. 
Mountain Limestone, Northumberland. 
7. Lingula maiiginata. —The Marginated Lingula, pi. 
XLIX. fig. 12. 
Lingula marginata. Phillips, II. p. 221, pi. 11, fig. 16. 
Much elongated, truncated in front, retrally rounded; edges 
of the valves turned up; sides parallel; valves flattened on their 
centres, with an elevated mesial ridge; whole surface covered 
with small, oval, hollow, fine, concentric and radiating stria?. 
The Mountain Limestone at Bowes. 
8. Lingula scutiformis —The Scuttle-shaped Lingula, 
pi. XLIX. fig. 20. 
Lingula parallela. Phillips, II. p. 221, pi. 11, fig. 18. 
Scuttle-shaped; truncated behind, and produced in front; sur¬ 
face smooth, with nearly obsolete lines of growth; sides almost 
parallel. 
