BIVALVES. — CHAMA. 57 



The American, Indian, and Atlantic Oceans; and the 

 Mediterranean, Caspian, and Adriatic Seas, produce infi- 

 nite varieties of this genus. 



CHAMA— C/am. 



Division I. — Shell equivalve. 



Family 1. — With longitudinal ribs, gaping at the posterior slope. 

 Gigas — Giaiit. Hippopus — Spotted. 



Family 2. — ■ With longitudinal ribs, posterior slope closed. 

 Antiquata — Antiquated. Calyculata — Variegated. 



Ajar — Ajar. Pectunculus — Peduncle. 



Trapezia — Trapeziform. Satiata — Obsolete. 



Rosea — Rose-coloured. Rugosa — Rugged. 



Family 3. — Shell longitudinally ribbed, having an ovate 



chamber in the interior of each valve. 



Concamerata — Chambered. 



Family 4. — Shell decussated, or transversely striated, without 

 ribs. 

 Semiorbiculata — Brown. Oblonga — Oblong. 



Cordata — Heart-shaped. Coralliophaga — Coral. 



Family 5. — Shell tuberculated. 

 Plumbea — Leaden. 



Family 6. — Heart-shaped, umbones prominent, and apices 

 spirally recurved. 

 *Cor — Heart. Moltkiana — Moltkian's. 



Division II. — Shell inequivalve. 



Lazarus — Lazarus. Lamellosa — Lamellar. 



Gryphoides — Gryphus. Punctata — Dotted. 



Cornuta — Horned. Sinistrorsa — Reversed. 



Sessilis— -aJc^/?/. A^rcmeWdi— Hedge- Hog, 



Ponderosa — Heavy, 

 d3 



