102 



« MODIOLA. 

 MYTILUS MODIOLUS. LintlCBUS. 



Mawes Linn. pi. \6 t fig. 1. 



Linjmsus and other writers have blended this genus 

 with that of the G. Mytilus. Lamarck has however 

 pointed out sufficiently strong characteristic distinc- 

 tions to authorize their being formed into a separate 

 genus. The shape of the shell is more transverse than 

 longitudinal; the umbones not being absolutely termi- 

 nal, it is rarely attached by a byssus to other substance?, 

 though it has the faculty of spinning one, in common 

 wilh the G. Mytilus, like which also, the valves 

 slightly gape; the cardinal ligament is almost whol- 

 ly interior, and occupies a marginal canal. Shell sub- 

 transverse, equivalve, regular, the posterior side very 

 short; apices almost lateral, and inclined to the shortest 

 side : hinge lateral and linear, without teeth; cardinal li- 

 gament almost entirely internal, affixed to a marginal 

 gutter; a muscular impression, sublateral, lengthened, 

 and hatchet-shaped. 



Modiola papuana Modiola Guyanensis 



tulipa Adriatica 



albicosta pulex 



