CONCHY LI A— DITHYR A. xix. 



23. Mactra. — Denies laterales transversim laminosi, vdlvtB 



alterius didymi. 

 The lateral teeth transverse and laminar, those of 

 one valve double. 



21. Lepton. — De?ites laterales valvce alterius transversim. 

 bipartiti. 

 The lateral teeth of one valve deeply cloven 

 transversely, 



40 NUCULA. — Denies primarii cochleariformes, lateralibus 

 numerosis. 

 The primary teeth spoon-shaped, with numerous 

 lateral ones. 



19. Kelli A.— P^a/ra altera dentibus duobus approximatis, altera 

 dente erecto concavo. 

 In one valve two teeth close together, and a single 

 erect concave tooth in the other. 



24. GOODALLIA. — Valva altera dente unico, altera dentibus duobus 



cum Joved trigond interpositd. 

 In one valve a single tooth, in the other two 

 teeth with a triangular cavity between them. 



•By 





