xxviii. GO^GEYLIA—DITHYRA. 



6. pellucidus, subarcuatus, dente altera bipartito. 



slightly curved, with one of the two teeth deeply 

 cloven. 



26. PsAMMOBIA. 



* valvd altera hidentatd. 



with two teeth in one of the valves. 



1. toeniata, dente altera planata-rotundato. 



one of the two teeth flattened and rounded. 



2. florida, striis minimis langitudinalibus reticulata. 



reticulate by minute longitudinal striae. 



3. costulata, antici costulis obliquis. 



with oblique ribs on the anterior side. 



4. fragilis, striis transversis lamellatis. 



with transverse laminar striae. 



5. Laskeyi, faved transversd elongatd cardinali. 



with a transverse elongated cavity at the hinge. 



** valvis bidentatis. 



with two teeth in each valve. 



9.' Legumen, lineari-ablanga, dente altera bipartita. 



linear-oblong, with one of the teeth deeply cloven. 



7. declivis, oblanga, dente altera concavo. 



oblong, with one of the teeth concave. 



8. antiquata, reniformis, dentibus conico-erectis. 



kidney-shaped, with the teeth conic and erect. 



