74 



CONCHOLOGY. 



M. hamatus."* 

 M. croceus.* 

 M. cubitus.* 



M. lateralis.* 



M. Californianus.* 



M. leucophoeatus.* 



2. Genus Modiola. PI. VIII. 



Animal. As above. 



Separated by Lamarck from the Mytilus, on account of its 

 being more transverse than longitudinal, the beaks instead of being 

 terminal are placed beneath the apex. 



Shell. Smooth, subtransverse, equivalve, regular, subtriangu- 

 lar, posterior side short ; summits nearly lateral ; hinge toothless, 

 linear and lateral ; ligament partly interior, situated in a marginal 

 furrow ; one sublateral, elongated muscular impression in each 

 valve. Inhabits the British and American seas. Thirty -two 

 species. 



Modiola Guyanensis. 

 M. pulex. 

 M. discors. 

 M. cinnamorea. 

 M. plicata. 

 M. lithophaga. 

 M. Adriatica. 

 M. discrepans. 

 M. trapezina. 

 M. silicula. 

 M. semen. 

 M. laevigata. 



Modiola Papuana. 

 M. tulipa. 

 M. albicosta. 

 M. vagina. 

 M. picta. 

 M. sulcata. 

 M. plicatula. 

 M. semifusca. 

 M. purpurata, 

 M. barbata. 

 M. caudigera. 

 M. squamosa. 



M. securis. 



M. Americana.* M. capax.* 



M. castanea* M. recta.* 



M. opifex.* M. Carolinensis.* 



M. semi-costata.* 



3. Genus Pinna. PI. VIII. 

 Animal. Body oval, elongated, moderately thick, enveloped in 



