Lamarck's Genera of Shells. 33 



2. Mytilus *. 



Shell longitudinal, equivalve, regular, pointed at the base, 

 fixed by a byssus. Beaks almost straight, terminal, pointed. 

 Hinge lateral, usually without teeth. Ligament marginal, sub- 

 internal. One elongated, clavate, sublateral muscular im- 

 pression. 



Linnaeus confounded the ostrese, aviculse, anodontse, &c., with 

 mytili, though the two first, are inequivalve and foliated, and 

 the last, fresh-water shells. 



The mytili are all sea shells, not foliated, nor gaping at the 

 superior margin, in which they differ from the pinna, which 

 in other respects they a good deal resemble. Their byssus is 

 short, with thick or coarse filaments, which they attach and de- 

 tach by means of a linguiform foot. They have a rather slender 

 adductor ligament in the upper internal part of the shell, an- 

 swering the same purpose as that of the modiola ; and another 

 ligament, pretty much like the former, in the base of the shell, 

 near the beaks, to strengthen the connexion of the valves at the 

 hinge. 



The species are subdivided into, (1) Shells longitudinally 

 furrowed, — II species, — and (2) Those having no longitudinal 

 furrows, 24 Species. 



Type. Mytilus Magellamcusf. 

 Shell oblong, angular and whitish below; purplish violet 

 above, with thick, wavy longitudinal furrows; nates acute, 

 nearly straight. Streights of Magellan. In all 35 recent spe- 

 cies, and 2 fossil. PI. I . Fig 79. 



3. Pinna J. 



Shell longitudinal, cuneiform, equivalve, gaping at the sum- 

 mit, base pointed, beaks straight. Hinge lateral, without teeth. 

 Ligament marginal, linear, very long, almost internal. 



The pinnae are sea shells, generally very large, thin in pro- 

 portion to their size, often brittle ; upper margin rounded some- 



• Original Latin name for the muscle shell fish. 



♦ From tlie Straits of Mu'^dlan. 



t nma, innnii, a kind ot .'ihcll lish, also d plume, vvhencc the name. 

 Vol. XV. D 



