72 BIVALVES. — MYTILUS. 



MYTILUS— il/«5c/e. 



Division I. — Shell oblong, umbones or apices ter- 

 minal AND POINTED, SLIGHTLY ANGULATED AT ONE 

 SIDE, AND ROUNDED AT THE LOWER MARGIN. 



*Edi\x\is ^Eatable. Latus — Broad. 



*Pellucidus — Pellucid. Perna — Lengthened. 



Vulgaris — Small. Smaragdinus — Green. 



Bilocularis — Two-celled. Confusus — Wedge-sJiap'd. 



Ungulatus — Ox-hoof. Bidens — Double tootlid. 



Exustus — Rose-coloured. Puniceus — Ventricose. 



Striatulus — Striated. Demissus — Silvery. 



Niger — Black. ' Ruber — Red. 



Division II. — ^Transversely ovate, with longitudinal 



RIBS on each side, AND PLAIN OR STRIATED 

 IN THE MIDDLE. 



*Discrepans — Compartment. *Discors — Discordant. 



Impactus — Wool' coated. 



Division III. — Found burrowed in rocks, corals, &c. 



Lithophagus — Burrowing. *Praecisus — Truncated. 



Aristatus — Crossbeak'd. Fuscus — Brown. 



*Ambiguus — Ambiguous. Plicatus — Plaited. 



*Rugosus — Rugged. Niveus — Snow-white. 



Coralliophagus — Coral-piercer. Arborescens — De7idritical. 



Division IV. — Shell oblong, gibbous, with the pos- 

 terior side dilated and elevated above 

 the hinge, apex rounded. 

 ♦Modiolus — Great. 



Division V. — Only found in fresh water. 



*Cygneus — Swan. *Anatinus — Duck. 



Fluviatilis — River. *Fucatus — Avon. 



Stagnalis — Stagnant. Dubius — Doubtful. 



Americanus — American. 



