Baker— The Molluscan Fauna of McGregor, Iowa. 2 55 



Symphynota complanata Barnes. 



Common. Eighty-seven per cent of the specimens of this 

 species contained pearls or pearly secretions. 



Margaritana monodonta Say. 



Very rare. Only two specimens were obtained from the 

 gigantic quantity of shells held by the fishermen, who call 

 this species the spectacle case. 



Unio gibbosus Barnes. 



Apparently not abundant. The nacre of the specimens 

 from this locality varies from white and lavender to deep 

 purple. No evidences of pearly secretions were found in 

 these shells. 



Unio crassidens Lamarck. 



Common. One small injured shell was collected. 



Pleurobema aesopus Green. 



Apparently rare as but one specimen was found. 



Quadrula plicata Say. 



Common. No pearly secretions were found in the shells 

 of this species, but several distorted shells were collected. 



Quadrula heros Say. 



Common. The nacre of this species varies from white to 

 white tinged with pink. Only a very few specimens showed 

 evidences of abnormal pearly secretion. 



Quadrula lachrymosa Lea. 



Not common. The specimens obtained are rounder than 

 normal lachrymosa. Only five specimens were obtained and 

 none of these showed pearly secretions. 



Quadrula matanevra Kafinesque. 



Only half a valve of this species was secured. 



Quadrula pustulosa Lea. 



Very common. Pearly secretions rare. These shells, of 

 which a large number were obtained, well illustrate the large 



