74 CONCHOLOGY. 



M. hirsutus. The bearded Mytilus. 

 Species with grooves ; covered with a shaggy or bearded 

 epidermis. 



2. Modiola. Twenty-three species. 

 Taken by Lamarck from the Mytilus, as it differs by 

 being more transverse than longitudinal, and the beaks, in- 

 stead of being terminal, are placed beneath the apex. 



Shell smooth, sub-transverse, equivalve, regular, sub-tri- 

 angular, the posterior side short; summits almost lateral; 

 hinge lateral and linear, without teeth ; ligament partly in- 

 terior, placed in a marginal furrow ; one sub-lateral elongated 

 muscular impression in each valve. 



Modiola Papuana. Modiola Guyanensis. 



M. lulipa. M. Adriatica. 



M. albicosta. M. pulex. 



M. vagina. M. discrepans. 



M. picta. M. discors. 



M. sulcata. M. trapezina. 



M. plicatula. M. cinnamomea. 



M. semifusca. M. silicula. 



M. securis. M. plicala. 



M. purpurata. M. semen. 



M. barbata. M. hthophaga. 



M. caudigera. 



M. discors. The discordant Modiola. 



Shell elongated oval, very convex, narrowest at the ante- 

 rior end; striated at the two extremities; summit oblique; 

 exterior greenish ; interior white, with sometimes a pink- 

 tinge, and somewhat pearly ; crenulated margin. ' 



M. Papuana. The Papuan Modiola. PL 12, fig. 6. 

 Species smooth, more or less triangular ; summit near the 

 anterior extremity ; byssus obsolete in adults. 



M. sulcata. The furrowed Modiola. 

 Species striated longitudinally. 



