Mya. 
MOLLUSCA. MYAD^. 
m 
Length about 2 inches, breadth 3 inches ; white, with a thin cuticle often 
of rusty colour ; concentrically striated ; smooth in the middle ; the broad 
vertical tooth has usually an oblique rib from the beak to its retral angle, and 
is marginated anteally ; the pit in the opposite valve for the ligament is hori- 
zontal, with a small tooth or projection on its an teal margin. The animal 
is frequently used as food, when boiled. In Zetland it is so used, and is call- 
ed Smurslm. 
577. M. arenaria. — Shell rounded at both extremities ; the 
retral one slightly produced and attenuated. 
Linn. Syst. i. 1112. Penn. Brit. Zool. iv. 79. t. xlii. Mont. Test. Brit. 
30. Turt. Biv. Brit. 32.— Common near low water-mark, lodged in 
sand or gravel. 
Length sometimes reaching 3 inches, breadth five and a half ; it chiefly dif- 
fers from the last in the production of the posterior extremity, by the presence 
of a few obsolete longitudinal ridges, in being more compressed, and the tooth 
rounder, syphon impression more conical — This species, called at Southamp- 
ton Old Maids^ and at Cork Sugar Lootis, is more frequently found in estuaries 
under the influence of fresh water, than the preceding. The M. ovalis of Dr 
Turton, Biv. Brit. 33. t. iii. f. 1, 2, seems nothing more than the young of M. 
arenaria, “ with the tooth flattened at the top, and flexuous.” 
578. M. Norwegica. — Dorsal margin nearly straight, waved 
and truncated retrally, rounded anteally. 
Turt. Linn. iv. 178 — M. striata, Mont. Linn. Trans, xi. 188. t. xiii. f. 1. 
— M. peUucida, Brown., Wern. Mem. ii. 505. t. xxiv. f. 1 — Lyonsia 
striata, Turt. Biv. Brit. 35. t. iii. f. 6, 7- — English and Irish coasts. 
Length half an inch, breadth an inch ; thin, semitransparent, with a brown 
cuticle, rugged retrally ; longitudinally striated ; inequivalve. According to 
Dr Turton (whom I have followed in bringing together the preceding syno- 
nims, not, however, without considerable hesitation), the tooth is an indepen- 
dent process, moveable with the ligament. 
579. M. decussata.—Ovsiie, with irregular concentric ridges, 
decussated by regular longitudinal striae. 
Mont. Test. Brit. Sup. 20 — .Frith of Forth, Mr Laskey. 
Diameter about half an inch ; white ; margin waved ; umbo-obtuse, re- 
curved, and placed nearest to one end ; a tongue-shaped syphon mark ; in one 
valve a broad erect tooth, in the other a projecting plate, with a small inden- 
ture for the reception of the tooth of the opposite valve. Its generic relations 
uncertain. 
EXTINCT SPECIES. 
1. M. mandihula Gibbose, flattish in the middle, transversely undulated ? 
retral side square, gaping, anteally straightish. — Sower. Min. Conch, t. xliii. 
In Green Sand. 
2. M. intermedia — Depressed, smooth, twice as wide as long ; sides round- 
ed, the anteal one small, the retral one expanded and gaping a little — Sower. 
Min. Conch, t. Ixxvi. f. 1, and t. ccccxix. f. 2 — London Clay. 
3. M. p/a7^a.— Rather depressed, smooth ; wider than long ; ovate ; nearly 
equilateral ; retral side rather elongated. — Sower, Min. Conch, t. Ixxvi. f. 2.— 
Plastic Clay. 
