CONCHIFERA. 



307 



ternal. Animal unknown ; without byssus. — 6 species ; 

 also fossil. 



Vulsella lingulata. 



These shells are not attached, but are found buried in 

 sponge in the Indian Ocean. They are iridescent within, 

 and extremely irregular in form, so as to make it very 

 difficult to distinguish the species. 



Myalina. Koninck, — Shell equivalve, inequilateral, 

 lengthened or oblique, with straight or slightly curved 

 hinge margin, which is without teeth; the ligament is 

 internal, and is received into a broad facet, having a 

 great number of little furrows parallel to the hinge 

 margin ; bosses pointed, terminal, or extending forward, 

 usually small, somewhat curved ; and immediately under 

 the same, in the interior, is a small plate like a partition, 

 as in Dreyssina ; muscular impressions doubtful. — Fossil. 



Ambonychia. Hall. — Shell equivalve, inequilateral, 

 compressed, winged behind, or slightly winged, at the 

 front edge blunt and suddenly sloped, or curved down- 

 wards ; the common form is somewhat obliquely oval, 

 swelled out towards the bosses ; the hinge border is very 

 oblique, approaching to a line which runs in the direction 

 of the curved bosses; the upper surface has raised con- 

 centric stripes, strong undulations or fine rayed lines ; the 

 muscular impression is large. — Fossil. 



