Myarta. | 
length, forming acute angles, their origin close to the cardinal 
hiatus, with the inner limb continued by a rib similar to that 
on the opposite valve. 
1. Lepron squamosum, pl. XL, f. 7. 
Psammobia punctura, First Ed., pl. 16, f. 7; Lepton squa- 
mosum, Turton, Biv., p. 62, pl. 6, f. 1, 2, 3; Fleming, p- 
429; Solen squamosus, Montagu, p. 565; Maton and Rackett, 
p- 48. 
Shell compressed, a little transversely elongated; both sides 
equally rounded; pellucid, thin, and white; whole surface 
covered with minute and thickly studded punctures, having 
much the appearance of shagreen when viewed through a 
strong lens; inside smooth, glossy, white, with obscure, longitu- 
dinal, radiating strie, diverging from the hinge. Length four- 
tenths of an inch; breadth half an inch. 
First met with in sand from Salcomb Bay; ‘Turton mentions 
Torbay; and Mr. Lyons found it at Tenby. 
2. LEpTON NITIDUM. 
Lepton nitidum, Turton, Biv., p. 63. 
“Shell glossy, slightly striate transversely. 
“Shell half the size of the last, which it resembles in shape 
and hinge, but is of a lucid, pale, glossy horn-colour, without 
punctures. 
“From coralliues, in Torbay.”— Turton. 
Genus 39.—Macpata.—Leach. 
Shell generally thin, transverse, inequivalve, inequilateral, 
gaping at the anterior side; hinge with a transverse, heart- 
shaped, unattached plate-like tooth, to which both valves are 
united by a small cavity on which this laminar plate is seated, 
and fixed by a ligamentary process; destitute of lateral teeth; 
ligament internal. 
1. Macpata striata, pl. XLIV, f. 1, 2, and 10. 
Magdala striata, First Ed., pl. 11, f. 1, 2, and 10; Aya 
Norwegica, Wood, Cat., p. 11; Fleming, p. 463; Mya pellu- 
cida, Brown, Wernerian Mem., II, p. 504, pl. 24, f. 1; Lyonsia 
striata, Turton, Biv., p. 35, pl. 3, f. 6, 7. 
Shell thin, subpellucid, transversely oblong; hinge line nearly 
parallel; anterior side shortest, and well rounded; posterior side 
truncated, gaping, and with the edges reflected; from the base 
of the truncation the shell abruptly obliques, until it reaches 
the basal line; umbones not quite central, very obtuse, and 
straight; surface covered with a thin, olivaceous epidermis, with 
pretty strong, concentric wrinkles, which are more strongly 
developed at the sides, especially the truncated one, where 
they are rugose and sharp; beneath the epidermis the shell 
is thickly beset with fine, longitudinal, slightly waved strizx, 
which is less strong towards the disks of the valves; inside 
of a rich pearlaceous hue, exhibiting iridescent reflections. 
Length about five-eighths of an inch; breadth an inch and a 
quarter. 
First discovered by Miss Hutchins, in Bantry Bay, Ireland, 
has since been found at Warren Point; at Tenby, Wales; and 
the Western coasts of England. 
MOLLUSCA. 
ill 
Genus 40.—MyatTE.ita.—Brown. 
Shell thin, transversely oblong-ovate, inequilateral; hinge line 
nearly parallel, truncated at one side; hinge with a large, single, 
erect, spear-shaped tooth in one yalve, resting upon a corres- 
ponding cavity in the cardinal region of the other valve; mar- 
gins smooth and even. 
1. Myatreitra Montacul, pl. XL, f. 26, 27. 
Hiatella striata, First Ed., pl. 16, f. 26, 27; Myatella stri- 
ata, Brown, Conch. Text Book, p. 142, pl. 16, f. 12 and 30; 
Mya striata, Montagu, Linn. Trans., XI, p. 188, pl. 13, f. 1 a ; 
Lyonsia striata, Turton, Biv., p. 35. 
Shell transversely elongated, thin, semitransparent; umbones 
short, obtuse, and situated nearest the posterior or truncated 
side, which is shortest; anterior side rounded; whole surface 
covered with a very thin, olivaceous epidermis, beneath which 
the shell is finely striated longitudinally, and is of a pearly hue; 
inside smooth, pearlaceous, and exhibiting nacred reflections. 
Length half an inch; breadth an inch. 
Discovered in Tenbay-bay, by Mr. George Lyons. 
It is not without considerable hesitation that I have instituted 
this genus, but I think it impossible that so accurate an observer 
as Montagu could describe the tooth of this shell as fixed, if it 
had not been so. Our figures are copied from his. Dr. Fle- 
ming says he followed Turton in bringing together the syno- 
nims, but with considerable hesitation. 
Genus 4]1.—Mya.—Linneus. 
Shell transverse, nearly equivalve, gaping at both extremities, 
but widest at the posterior side; one valve with a large, com- 
pressed, dilated, hollow, spoon-shaped, perpendicular, vertically 
projecting tooth; the opposite valve destitute of teeth; the 
cartilage placed in a narrow suture; two lateral, distant, large, 
muscular impressions, the anterior one narrow, and the posterior 
almost orbicular; pallial impression with a large sinus; ligament 
internal, large, and fixed in the cavity of the tooth in one valve, 
and to a large subumbonal cicatrix in the other. 
1. Mya arenarta, pl. XLV, f. 1. 
Mya arenaria, First Ed., pl. 10, f. 1; Montagu, p. 30; 
Donovan, II, pl. 85; Lamarck, V, p. 461; Turton, Biv., p. 
32; Fleming, p. 463. 
Shell strong, transversely oblong-oval, and moderately con- 
vex; umbones rather large, prominent, nearly central, and not 
incurved; one side more ample and rounded than the other, 
which is somewhat acuminated, and pointed at the extremity ; 
external surface generally with concentric wrinkles and irregular 
strie, mostly of a brownish sand-colour, but differing considera- 
bly from various localities, as well as from the age of the shell; 
one valve with a broad, thick, perpendicular tooth, provided 
with a large spoon-like cavity for the reception of the cartilage, 
and another smaller one by its side; opposite valve destitute of 
teeth; inside glossy, white. 
Inhabits many of the British and Irish coasts, particularly at 
the mouths of rivers. 
2. Mya truneata, pl. XLV, f. 2. 
Mya truncata, First Ed., pl. 10, f.2; Montagu, p. 32; Dono- 
van, III, pl. 92; Maton and Rackett, p. 35; Turton, Biy., p. 
31; Forbes, p. 54. 
