CONCHOLOGY. 73 



or less curved, a little sloping inferiorly ; hinge generally 

 without teeth, or with two very small rudimentary teeth ; 

 ligament dorsal, linear, sub-interior, inserted in a long and 

 narrow furrow ; two muscular impressions, of which the an- 

 terior is very small, with or without longitudinal grooves or 

 furrows. 



Mytilus Magellanicus. Mytilus exustus. 



M. erosus. M. bilocularis. 



M. crenatus. M. ovalis. 



M. decussatus. M. ustulatus. 



M. hirsutus. M. Domingensis. 



M. elongatus. M. Senegalensis. 



M. latus. M. Afer. 



M. zonarius. M. achatinus. 



M. ungulatus. M. ungularis. 



M. violaceus. M. planulatus. 



M. opalus. M. borealis. 



M. smaragdinus. M. Galloprovincialis. 



M. corneus, M. angustanus. 



M. edulis. M. lineatus. 



M. retusus. M. lacunatus. 



M. Hesperianus. M. canalis. 



M. perna. M. incurvatus. 

 M. abbreviatus. 



M. incurvatus. The incurvated Mytilus. 

 Nearly smooth, elongated oval, valves inflated and curved 

 near the ligament ; apex acute. 



M. Afer. The African Mytilus. 



More or less compressed and sub-triangular, without 

 grooves ; byssus very large and much developed ; summit 

 entirely terminal and anterior; smooth and radiated witli 

 blue or purple, covered with a dark brown epidermis ; inside 

 margin blue, shade decreasing to the centre. 



M. crenatus. The crenated Mylilus. 

 Species longitudinally gooved, radiated, or striated. 

 K 



