176 WORMS. TESTACEA. 56. Mya. 
Inhabits frefh rivers of Zuzope, z) Barbary, 6) Tranguebar, and 
is the fhell whieh i is commonly ufed to put warer- colours in : 
12 inchlong, 3i broad; covered with a brownifh or blackifh 
coat, and under this yellowifh or greenih, with green rays; 
within fmooth and clay-colour: very thin and brittle, and 
does not gape at either end. 
* Margari- Spell ovate, a little contracted in the middle of the thinner 
tifera. margin: primary tooth of the hinge conic: protubes 
rant parts near the hinge decorticated. 
Brit. Zool.iv tab. 43, f. 18. Barbut, tab. 2, f. 2. 
Lifier conch. tab. 149, fiz. 4. 
Lifter Anim. Angl. app. tab. 1, fig... 
Gualt tab 102, fig. C. Tiled. tab. 10, f. id 
Knorr. Vergn 4. tab. 25, ia . 
Chemn conch. 6. tab. Y. fig. 
Inhabirs moft parts of the dre circle, and is generally found in 
Moen noes rivers and about cataracts; about 5 inches broad 
and 22 long: /beil/ thick, coarf+, opake, tranfverlely wrinkled, 
black on the outfide, and o'ten corroded by worms: hinge 
without lateral teeth, the primafy tooth being received into a 
broad cleft tooth of the oppofite hinge. 
'This fhell is noted for producing large quantities of mother of 
pearl and pearl, thefe latter being a difeafe of the fifh analo- 
gous to the ftone in the human body. The river Conway in 
Wales was formerly famous for producing pearl of great fize 
and value, 
Perna. Shell oblong, dilated, the narrower bal compreffed, 
Knorr, lergn. 4. tab. Y5, fig. 2. 45 5. 
Chemn. conch. 8. tab. 85, f 738, 739. 4. 84, f. 748. 
Schrat. Einl conch. 2. tab 7, fig. 4. 
Inhabits the Magellanic Straits and fhores of Barbary ; refembiles 
a ham or leg of mutton: hell fmooth, blue and white, open at 
one end: infead of the singe is a deep tranfverfe hollow, in 
the middle of which is a fharp tooth in each valve: probably 
not of this Genus. 
Pullla. * Shell tongue-fhaped; the hinge terminal, depreffed and 
femiorbicular. 
Lifter conch, tab. 1055. f. 10. 
Rumpf. Muf. tab. 46. fig. A. Gualt. tab. go. f. H. 
Valent. Muf. tab. 16. fig. 28. — Barbut. tab. 2. f. 5. 
Knorr. Vergn. 8. tab. 2, fig» 1—3. 
Chemn. conch. 6. tab, 2. fig. 8—11. 
Inhabits the Indies: 1$ inch droadg 4 inches long. 
Shell varying in form according toitsage: the valwes rather flat, 
gaping, finely ftriate tranfverfely, outwardly yellowifh radiate 
with blackifh and yellowifh: sooth Yong, broad and grooved 
along the middle: probably not of this Genus. 
