xxvi. CONCHYLIA—DITHYRA. 



2. elliptica, lateribus rotundatis. 



rounded at both ends. 



23. Mactra. 



* dentibus laterlibus striatis. 

 the lateral teeth striate. 



1. solida, ovato-trigona, cequilateraJis, I(sviuscnla. 



oval-triangular, equilateral, and smooth. 



2. truncata, trigona, eequilateralis, lateribus truncatis 



triangular, equilateral, truncate at the sides. 



3. cpssa, trigona, imequilateralis leeviuscula. 



triangular, inequilateral, nearly smooth. 



4'. subtruncata, ovato-trigona, incequilateraUs, transversim sulcata. 

 oval-triangular, inequilateral, grooved trans- 

 versely. 



6. deaiu'ata, oblonga, incequilateralis, transversim rugosa. 



oblong, inequilateral, transversely wrinkled. 



** dentibus lateralibus Icevibus. 

 with the lateral teeth smooth. 



6. Stultorum, eequilaterulis, transversim subslriata. 



equilateral, and slightly striate transversely. 



7. cinerea, sub(Equilateralis, Iceviuscula. 



nearly equilateral and smooth. 



8. glauca, infequilateralis, transversim striata. 



inequilateral and striate transversely. 



