72 BIVALVES. MYTILUS. 



MYTILUS Muscle. 



DIVISION I. SHELL OBLONG, UMBONES OR APICES TER- 

 MINAL AND POINTED, SLIGHTLY ANGULATED AT ONE 

 SIDE, AND ROUNDED AT THE LOWER MARGIN. 



*Edulis Eatable. Latus Broad. 



*Pellucidus Pellucid. Perna Lengthened. 



Vulgaris Small. Smaragdinus Green. 



Bilocularis Two-celled. Confusus Wedge-shap'd. 



Ungulatus Ox-hoof. Bidens Double tooth'd. 



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 Dendritical. 



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. 



