1893.] Mollusks of Louisiana. 955 
specimen in Castor Bayou, Catahoula Parish, that I take to be 
of the same species. 
Unio mississippiensis Conrad, is abitdent! in the ponds and 
creeks throughout the section. It was found in Dorcheat 
Bayou and in Bayou Pierre, but is usually not abundant in 
the larger streams. "The species does not present very much 
variation. 
Unio hydianus Lea, is found in all of the larger bayous in 
which I collected—Dorcheat, Corney, eic. The specimens are 
very numerous. The variation is great, from individuals that 
are sub-compressed, to those that are very much inflated. 
There is a marked tendency to become much inflated in old 
age forms. ‘The number and size of the rays vary much, some 
specimens have wide rays, others narrow rays, and still others 
are scarcely rayed at all. This species, on account of its enor- 
mous amount of variation, is one of our most attractive and 
instructive forms. 
Unio approximus Lea. A specimen of this species was found 
in a small creek in Rapides Parish. We think that we are not 
alone when we consider the difference between hydianus and 
approximus almost nominal. 
Unio obtusus Lea, was collected by Mr. O. B. Lewis in a 
branch near Burk Place, in Bienville Parish. Mr. C. T. Simp- 
son so determines a specimen that I sent him, and from Lea's 
figures and descriptions I would so consider it. 
Unio parvus Barnes, is found in a good many of the bayous. 
It is almost impossible, if not entirely so, to separate this and 
the three following species, but a good many of my specimens 
seem undoubtedly parvus. | 
Unio texasensis Lea, abundant everywhere that I collected 
Unionide, except in Red River, Cross Lake, and a few very 
small creeks. These specimens can be gathered by thousands. 
The variation is enormous, from elongated to rather short; 
from thin to rather thick shelled, etc. 
Unio bairdianus Lea, is considered a synonym of the above. 
It is abundant in the creeks of the section. 
Unio bealei Lea, were collected in the creeks around Mt. 
Lebanon. This form is extremely close to texasensis. 
