WORMS. TESTACEA. 49. Pinna. 165 



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

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

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

 a variety of the last. 



3 16. M. Cygneus. Oval, thin, brittle, transversely wrin- 

 kled, rounded and compressed at one end* produced 

 at the other: hinge lateral. 



Er. Zool. t. 67. /. 78. Donovan f, 55. L. Trans, viik t. 3. A.f. 2. 



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

 Linn. Trans vui.jfr. 109. tab* 3. A./. 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, venticose. 



317. M. stagnalis. Oval, rather smooth, gibbous, with 

 a flat space near the hinge. 



Souierby Brit. Miscell. 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. 

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

 and the margin is yellowish-brown. 



318. M. anatinus. Oval, rather compressed^ brittle, 

 semitransparent, with a membranaceous margin, de 

 corticated at the beaks. 



r. Zool. t. 68./. 79. Donovan t. 113, Da Cost, f. 15.7. 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. 4voerisis. Subpval, thin, wrinkled, olive-brown* 

 straight or slightly arched on the front margin. 



Montague p. 172. Linn. Trans, viii. p. no., tab. 3. A./. 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, stfiate^ with length- 

 ened beaks. 



Walker minute shells.fig. 75. Shell minute. 



49. PINNA. Nacre. 



321. P.pedinata. 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. i6./. 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 ks widU^the smooth side a little 

 gibbous on the margin, within smooth pearly. 



322. P. ingenx. 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 striae 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; 



