WORMS. TESTACEA. 4*. Pinna. TO9 



skin, is very slightly convex, rounded and broader at the end re* 

 mote from the hinge,, and has only 8 or 9 ribs on the side near the 

 beak which are double the number in M. difcofs. Is probably only 



a variety of the last. 



3I6* M. Cygneus. Oval, thin, brittle, transversely wrin- 

 kled, rounded and compressed at one end, produced 

 at the other : hinge lateral. 



Br. Zool. t. 67./. 78. Donovan t, 55. L. Trans, viii. t. 3. A.f. 2. 



2 much lefs, thick, ponderous, rough, sloping on the fore-part. 

 Linn. Trans \'\\\.p. 109. taAi 3. A.f. 3. 



Shell 2 inches and a half long, nearly 6 broad, covered with 

 an olive-green skin under which it is ochraceous or va- 

 ried with bright brown and sometimes radiate* within pearly- 

 white : beak very small, venticosc 



317. M* stagnate. Oval, rather smooth, gibbous, with 

 a flat space near the hinge. 



Sowerby Brit. Mhcell. tab. 16. 



Shell 4 inches and a half long, nearly 8 broad, covered with a 

 dark green skin and marked with darker rays: resembles M, 

 Cygnets but is larger, more gibbous, more pointed on one side, 

 and the margin is yellowish-brown. 



3 18. M. anatinus. Oval, rather compressed, brittle, 

 semitransparent, with a membranaceous margin, de 

 corticated at the beaks. , 



Br. ZooL t.68.f.jg. Donovan t. 113. Da Cost. t. 15./. 2. 



Shell 2 inches long, 3 and a half broad, resembles M Cygneus, 

 but is more comprefsed and rounded at the anterior end, and the 

 cartilage side extends in a straight line to an acute angle, and 

 thence continues in an oblique line towards the bottom » 



319. M. Avoensis. Suboval,thin, wrinkled, olive-brown, 

 straight or slightly arched on the front margin. 



Montague p. 172* Linn. Trans. v'u'x.p. mo... tab-. 3. , A.f. 4. 



Shell resembling the. last, but is much lefs, broader in propor* 

 tion to its length, not so much produced at the hinge, and the 

 posterior side is more produced and rounded. 



320. M. striatus. White, pellucid, striate, with, length- 

 ened beaks. 



Walker minute shells. fig. 7 5. Shell minute, 



49. PINNA. Nacre. 



321. P.pectinata. Thin, pellucid, light horn colour 

 longitudinally ribbed and spinous for half its width, 

 obliquely striate transversely on the other. 



Donovan t. 10. Da Costa t. lG.f. 3. P. muricata. 



Shell 6 inches and: a half long, 3 inches broad, tapering to the 

 tip and a little curved, rounded at bottom, clothed towards the 

 base with concave spines for half its width, the smooth side a little 

 gibbous on the margin,, within smooth pearly. 



322. P. ingens. Nearly triangular, horn-colour, smooth ; 

 longitudinally striate on one side, with very rough 

 scaly wrinkles on the broader end. 



Br. Zoel. n. 81. Donovan t. 152.. P. lasvis. 



Shell near 12 inches long and 7 broad, pointed and curved at the 

 tip. with fometimes a few faint longitudinal strise from the top, 

 and rarely with a few concave fpines; the lower-part rough with 

 laminated tranfverfe wrinkles. 



323. P. muricata. Thin, semipellucid, flesh-colour^ with 



