PLATE LIX. 
1. Ostrea Duriuscula. 
2. 0. Dorsata. {Bached Oyster.) Oblong; variable; convex ; beaks blunt; upper valve convex, 
vvitlx many, longitudinal, sub-imbricated, furcated striae; inner margin dentated. 
3. 4. 0. Obscura. {Obscure Oyster.) Oblong, irregular; beak obtuse, curved; liinge-area large, 
triangular; lower valve very deep; the other flat. 
5. 0. Inequalis. ( Unequal Oyster.) Surface very rugged; margins irregularly undulated; 
lines of growth waved. 
6. 0. Carinata. {Keeled Oyster.) Elongated, arcuated, inflated, pointed at both ends; sides 
flattened; with many, transverse sulci, and strong, angular ribs; centre, with keel; margin, with 
strong, tooth-like processes. 
7. 0. Semiplana. {Half-plain Oyster.) Oval; depressed ; surface foliated; valves flat in centre. 
8. 11. 0. Solitaria. {Solitary Oyster.) Obovate, thick; sometimes incurved; beaks short; with 
many, divergent, furcated ribs and deep sulci, crossed by rugged, imbricated laminae; one valve 
flatter than the other. 
12. 0. Pulchra. {Fine Oyster.) Orbicular, compressed; one valve convex, with obscure beak 
and many, radiating, flat ribs and shallow sulci, crossed by Avide-set laminae; the other valve flat, 
Avitli short, blunted, incurved beak; hinge-line parallel. 
13. Anomia Ephippium. {Saddle-shaped Anomia.) Sub-orbicular, irregularly waved and 
Avrinkled ; one valve conA r ex ; the other flat; perforation large. 
14. A. Undulata. {Waved Anomia.) Strong, flat, sub-orbicular, with many, strong, divergent 
striae ; umbo flat; perforation large. 
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