MOLLUSCA. 
107 
Mactracea.] 
are separated by a triangular hiatus, below the umbo; inside 
glossy, white. Length a little more than a quarter of an inch ; 
breadth nearly half an inch. 
Found at Belton Sands, near Dunbar ; and Turton says it 
inhabits the Western coasts. 
5. Tellimya glabra, pi. XLII, f. 20, 21. 
Tellimya glabra, First Ed., pi. 14, f. 20, 21. 
Shell elliptical, moderately inflated, thin, smooth, extremely 
glossy; umbones obtuse, placed considerably to one side; shorter 
side obliquely subtruncated, the other rounded ; hinge with one 
broad primary tooth in each valve, and a large hiatus immedi- 
ately under the umbones in both valves; inside smooth, glossy; 
margins sharp. Length nearly a quarter of an inch ; breadth 
about half an inch. 
Found by General Bingham, at Dunbar ; in his cabinet, and 
also that of Lady Jardine. 
6. Tellimya bident ata, pi. XLIV, f. 8, 9* 
A.natina bidentafa, First Ed., pi. 11, f. 8, 9; Montacuta 
bidentata, Turton, Biv., p. 60 ; Mya bidentata, Montagu, p. 44, 
pi. 2, f. 5 ; Brown, Ency. Brit., VI, p. 405. 
Shell suboval, thin, compressed, smooth, white, but not 
glossy ; umbones small, situate nearest to one side, and slightly 
bent ; hinge with two hroad, erect, laminated teeth in one 
valve, these stand obliquely outwards from the beak, and some- 
what distant from each other, between these, and immediately 
under the umbo, is a slight triangular cavity for sustaining the 
cartilage ; opposite valve with a triangular hiatus, situate imme- 
diately below the umbo, for the reception of the opposite teeth. 
Length an eighth of an inch ; breadth rather more. 
Found in Salcomb Bay, burrowing in decayed thick oyster 
shells. 
7. Tellimya substriata, pi. XL, f. 23. 
Tellimya substriata, First Ed., pi. 16, f. 23 ; Montacuta sub- 
striata, Turton, Biv., p. 59} ph 11, f. 9, 10; Ligula substriata, 
Montagu, Sup., p. 25. 
Shell suhovate, somewhat oblique, a little inflated, slightly 
contracted in the middle of the valves, subpellucid, white, 
sometimes with a ferruginous tinge ; umbones prominent, 
straight, and not quite central ; one side short and narrowed, 
the opposite ample and rounded; surface covered with elevated, 
distant, nearly obsolete striae ; hinge with a cleft side tooth, a 
narrow grooved tooth on the opposite side, and a hiatus 
between them, immediately under the umbo ; teeth in the 
opposite valve very indistinct, if any, with a central triangular 
hiatus. Diameter about the tenth of an inch. 
Found attached to corallines, on the Devonshire coast; and 
to spines of the Echinus purpureus, to which they are attached 
by slender filamentary processes, emanating from the middle of 
the margin. 
Section III. — Ligament internal; shell gaping at the sides. 
Genus 34 — Mactra. — Linnaeus. 
Shell generally thin, sometimes thick ; equivalve, for the most 
part nearly equilateral, and more or less regularly triangular ; 
slightly gaping at one end, and almost imperceptibly so at the 
other ; each valve with one V shaped cardinal tooth, the point 
being next the umbo, diverging from it, and in some species 
the limbs are disunited at the base, so as to give the appearance 
of two distinct teeth ; close on the posterior side is situate a 
very thin, sharp tooth ; immediately behind the angular tooth 
is placed the pit for the reception of the ligament, and project- 
ing somewhat within the shell; one valve with two lateral teeth 
on each side, and one on both sides in the other, diverging from 
the heaks, near the margin of the shell, and fitting into the 
space between the two in the opposite valve ; two lateral, 
remote, muscular impressions ; pallial impression with a small 
sinus; ligament consisting of two portions, the one considerably 
larger than the other and internal, and the other half external ; 
two strong, lateral, muscular impressions in each valve ; pallial 
impression interrupted by a small sinus. 
Section I. — Lateral teeth smooth ; shell fragile. 
1. Mactra glauca, pi. XLI, f. 1. 
Mactra glauca, First Ed., pi. 15, f. 1 ; Montagu, p. 571 ; 
Donovan, IV, pi. 125 ; Turton, Biv., p. 73 ; Fleming, p. 428 ; 
Mactra helvacea, Lamarck, V, p. 473. 
Shell suhtriangular, thin ; anterior side slightly wrinkled ; 
umbones somewhat obtuse, a little reflected, with a narrow 
intervening gap ; surface of a cream-yellow colour, very finely 
striated transversely, and with irregular, broad and narrow glau- 
cous radiations of a pale brown-colour ; inside of a pale cream- 
colour, or purple ; margins thin, and sharp. 
Found on the coast of Cornwall ; but I am not aware that 
any living specimens have been met with, the locality not 
having been yet detected. 
2. Mactra Stultorum, pi. XLI, f. 2. 
Mactra Stultorum, First Ed., pi. 15, f. 2 ; Montagu, p. 94 ; 
Donovan, III, pi. 106; Turton, Biv., p. 72; Maton and Rackett, 
p. 69. 
Shell suhtriangular, thin, semipellucid ; umbones central, 
rather prominent, and frequently of a purplish hue ; sides nearly 
equal; surface covered with a yellowish-brown, or fawn-coloured 
epidermis, frequently of a cream-colour, beneath which the shell 
is elegantly radiated with deeper brown, or brownish-purple, 
irregular in number, some broad, others narrow, and frequently 
with transverse zones of a paler colour ; inside pale lilac, which 
frequently penetrates to the outside, giving it the same cast of 
colour ; when the epidermis is removed, it is found to be 
covered with faint, somewhat irregular, transverse striae. Vary- 
ing in length from an inch and a half to nearly two inches ; and 
in breadth from one inch and three-quarters to nearly two 
inches and a half. 
This species is found on most of the British and Irish coasts. 
Some specimens are entirely destitute of rays. 
3. Mactra dealbeta, pi. XLI, f. 8, 9. 
Mactra dealbeta. First Ed., pi. 15, f. 8, 9 j Pulteney, Cat. 
Dorset, p. 31 ; Montagu, p. 95, pi. 5, f. 1 ; Maton and Rackett, 
p. 68, pi. 1, f. 10 ; Fleming, p. 429. 
Shell transversely ovate, thin, fragile, moderately inflated ; 
umbones not quite central, but situate nearer the larger side ; 
gaping a little at the narrower side ; colour grayish or brownish- 
white, very finely striated concentrically, and with a few coarser 
transverse wrinkles; middle tooth in one valve broad, cleft, and 
angulated close to the beak ; lateral teeth not very remote ; 
inside glossy, white ; margin plain, with a sharp edge. 
Found at Weymouth, by Mr. Bryer, but is extremely rare ; 
if it is not merely a variety of M. Stultorum. 
