PANAMIC-PACIFIC PELECYPODA 453 



Genus PAia)OKA Chemnitz, 1795 



Opinion 184, acceptance of Chemnitz's generic names, type species by 

 subsequent designation, Children, 1825, Tellina inaequivalvis Linne. Recent. 

 European seas. 



Shell transversely elongated, inequivalve, the right valve depressed, 

 flat or concave, the left valve convex, larger, overlapping the other along 

 the ventral margin. Inner layer of shell pearly, covered by a thin, prismatic 

 outer layer. 



The genus is divided into subgenera on basis of the hinge. 



I. Right valve with two crural teeth; an obscure tooth may be present in 

 the left valve. 



1. Lithodesma absent. Surface smooth or with growth lines only. 



Subgenus Pandora 



2. Lithodesma present. Right valve with radial markings. 



Subgenus Pandorella 

 II. Right valve with three teeth or crural laminae. 



3. Left valve with a posterior and anterior inverted V-shaped crural 

 lamina. Cavity within the pallial line usually with radial markings. 



Subgenus Frenamya 



4. Left valve with three crura, two in front, the other behind, slender, 

 elongated and parallel to the dorsal margin; below, it is bordered by 

 the resilifer groove. 



a. Posterior lamina separated from the margin by a deep groove. 



Subgenus Clidiophora 



b. Anterior lamina short, hooked at the end, the posterior lamina slender, 

 its anterior section united with the dorsal margin by a sheet or platform 

 which roofs over an empty space below. 



Subgenus Fovedens 



General key to species of Pandora in the southern Panamic province. 



I. Right valve having two crural laminae. 



1. Shell wide and high, subovate. Surface with radial markings. 



P. {Pandorella) rhypis 



2. Valves elongated and narrow; surface smooth. 



a. Anterior side with a deep, hook-shaped cut. 



P. {Pandora) uncifera 



b. Anterior side entire. 



P. {Pandora) hrevijrons 

 II. Right valve with two crural laminae. 



3. Left valve with two crural laminae. Cavity of shell within the pallial 

 line with radial markings. 



P. {Frenamya) radiata 



4. Left valve with three crural elements. 



c. Anterior lamina long and slender, touching the anterior adductor scar. 

 Anterior-dorsal margin serrated. 



P. {Clidiophora) arcuata 



d. Similar to the above but with the dorsal margin simnle. 



P. {Clidiophora) comuta 



e. Anterior lamina short, hooked. 



P. {Foveadens) panamensis 



