312 TESTACEOUS MOLLUSCA. 



on one or both sides (in characteristic examples saddle-shaped); 

 rather thick, purple : the hinge-ridges of nearly equal length, not 

 longer than they are separate from each other at the base. 5. 

 Java, &c. 



P. Papyracea. — Placenta Quadrangula, Retz,from Gualt. £.104, 

 f.B. — Ephippium, &c, P., Ch.f. 715, copied E. t. 174,/. 2. — Anomta 

 Sella, junior, D. p. 297. — P. P., Lam. 2. — Gray, Cat. Plac. p. 2. 

 Somewhat quadrilateral, nearly flat, thin, hyaline, brownish purple, 

 or subradiatingly mottled with purplish liver-colour and . white ; 

 hinge as in the last species. 4. Red Sea. Perchance the young of 

 Sella. 



P. Placenta.— Anomia P., Lin. Ubi.—Ch.f. 716.— D. p. 297.— 

 W. t. 12, /. 29. — Placenta Orbicularis, Retz. p. 15. — Gray, Cat. 

 Plac. 4.— P. P., Lam. 3.—E. t. 173, /. 3.— Crouch, t. 12,/. 11.— 

 Reeve, C. S. t. 122. — Woodw. t. 16, /. 6. Suborbicular, longer than 

 broad, becoming narrower towards the hinge, white, semitransparent, 

 not flexuous : ridges of the hinge very gradually diverging from each 

 other, of very unequal length ; scar not directly under the middle of 

 the hinge. 6. China. 



P. Lincolnii. Gray, Cat. Plac. 3. Flat, rather solid, subopaque ; 

 outline suborbicular, rounder before and behind : ridges of the hinge 

 elongated, nearly equal, longer than they are separate from each 

 other at the base, their angle not acute. Australia. 



ANOMIA. 



Inequivalve, irregular, attached by a plug, more or less nacreous 

 within: under valve with a large perforation near the umbo : upper 

 valves with 2 or 3 subcentral muscular impressions. 



* Upper valve with 3 subcentral muscular scars. 



A. Ephippium. Lin. 1150. — Lam. 1. — Turt. Biv. 227, pi. 18, 

 /. 1, 2, 3. — Br. Mol. 2, p. 325, pi. 55, / 2, 3, 5, 7. — A. Cepa, 

 Lin. 1151.— Poli, £.30, /. 1, 2, 5 to 8.— Lam. 3.— Turt. Biv. 228, 

 t. 18,/ 4. — A. Electrica, Lin. 1150. — Lam. 4. — Turt. Biv. p. 226, 

 t. 17,/ 8, 9.— A. Squamula, Lin. 1150. — Lam. 8. — Turt. Biv. 229, 

 t. 18, / 5, 6, 7.— A. Punctata, Ch. — Turt. Biv. pi. 18, / 11.— 

 A. Violacea, Cucullata, Brug. 70, 71. — A. Flexuosa, Rugosa, 

 Cylindrica, Gm. — A. Margaritacea, Poli. — A. Patellaris, Pyri- 

 formis, Fornicata, Lam. 2, 5, 6. — A. Cymbiformis, Mat. and Rac. 

 — A. Tubularis, Turt. — A. Coronata, Bean. — A. Polymorpha, 

 Scabrella, Phil. Moderately strong when mature, of very variable 

 contour, suborbicular in freely-developed examples, smooth, or with 

 slight concentric wrinkles (occasionally, from being moulded upon 



