Baker — The Molluscan Fauna of McGregor, Iowa. 250 
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 erpsosus 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 crassipens 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 Rafinesque. 
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 
