THE FAMILY NAIADES. 



51 



OVAL. 



trigona.* »^za?. 



radiata.t Spix. 



purpurea. Valen. 



Ferussaciana. Lea. 



salmonia. Lea. 



incerta. Lea. 



fluviatilis. Lea. 



Myt. fluviatilis4 Soland. Dill Wood. 

 Myt. illitus. Soland, 

 An. cataracta. Say. 

 An. implicata? Say. 

 An. teres. Con. 



glauca.§ Valen. 

 An. glauca. Lam. 



* Ferussac considered trigona as the same with crassa of Swainson. The 

 two figures, however, appear to me to be too different to be considered the 

 same. 



•j- The outhne of this species is very much like that of trigona, Spix, and 

 they may, perhaps, prove to be the same species. Ferussac considered it to 

 be the young of exotica, Lam., in which I cannot agree with him. 



\ See note on Jin. cygnea, page 49. 



§ The figure of this shell resembles some individuals of Myt. Jluviatilis, 

 Soland, (Say's Jin. cataracta,) but is straighter on the superior margin. In 

 this character it resembles the trapezialin. The observations of Barnes, being 

 made when little was known of this genus, cannot now be admitted. 



