Pandoridae and Lyonsiidae 57 



margin flattened; anterior margin round, truncate; ventral margin 

 rounded and prolonged; shell much narrowed toward posterior ex- 

 tremity; right valve flat, left convex, each with a narrow oblique 

 ridge near anterior extremity; oval impressions of two adductor 

 muscles, pallial line simple, discontinuous. 



Dredged in two fathoms off Blind Pass, Sanibel Island. 



Subgenus KEXJfERLIA Carpenter, 1864 

 Pandora bushiana''- Dall PI. 9, fig. 48 



Alt., 6; length, 14; diam., 1.5 mm. Shell white, smooth, delicate 

 epidermis; right valve flat or concave, left valve convex; inequi- 

 lateral, short and rounded anteriorly, prolonged posteriorly; umbos 

 minute; anterior and ventral margins rounded; posterior margin 

 extended, nearly straight; a linear demarcation between anterior and 

 posterior portions of valves; slightly carinate behind; sculpture of 

 growth Imes; hinge typical; pearly interior, two muscle scars; in- 

 distinct, simple palhal Ime. 



Dredged off Sanibel Island between four and six fathoms. 



Pandora arenosa*5' (Conrad) PI. 9, fig. 49 



Alt., 5.5; length, 12; diam., 1.5 mm. General features like P. 

 bushiana; shorter; with ventral margin more convex. Right valve 

 concave, with fine, radiating, engraved lines. Left valve convex, 

 smooth. 



Dredged in the Gulf with P. bushiana. 



Family LYO^^SIIDAE 



The family Lyonsiidae has genera in both the Atlantic and the 

 Pacific oceans, most of them in deep water. Shells are small, fragile, 

 and pearly. The lower west coast of Florida has two species of 

 Lyonsia. 



Genus LYONSIA Turton, 1822 



Lyonsia^* floridana Conrad PI- 9, fig. 50 



Alt., 7.5; length, 16; diam., 5 mm. Shell fragile and translu- 

 cent, pearly; thin papery epidermis; inequivalve, left larger, its 



8- Named for Katherine J. Bush. 



^^ Lat., arenosus, sandy. 



^* Genus dedicated to- tlie naturalist, W. Lyons. 



