1892.] Mollusks of Louisiana. 957 
of pustulosus approach very near to turgidus, and I am inclined 
to the opinion that these two forms connect by intermediate 
examples. 
Unio schoolcraftii Lea. Corney Bayou. Not very abundant. 
Unio nodiferus Conrad. Corney Bayou. Not very abundant. 
These specimens seem almost fac-similes of those in the Phila- 
delphia Academy of Natural Sciences collection from Neches 
River, Texas. 
Unio turgidus Lea. Dorcheat Bayou. Somewhat abundant 
in this stream. 
Unio pustulatus Lea. Caddo, and Cross Lakes, Lake Biste- 
neau. It is abundant in the two first lakes.‘ It varies very 
much in the amount of the development of the pustules. 
Unio houstonensis Lea, is found in the three larger lakes and 
Bayou Pierre. 
Unio trigonus Lea. Cross Lake, Bayou Pierre and Dorcheat 
Bayou. This species and the next two form a most interesting ` 
and a somewhat perplexing set of forms. 
Unio cerinus Conrad, is found abundantly in nearly all of the 
bayous and the larger creeks throughout northwestern Louisi- 
ana. Many hundreds of specimens were obtained from Corney 
Bayou. It varies enormously, and undoubtedly grades into 
the next species. 
Unio chunii Lea. Corney Bayou, Dorcheat Bayou, Cross 
Lake. It is somewhat abundant in Corney Bayou. It 
varies greatly, sometimes being arcuate on the base, almost 
hooked as the posterior margin is approached. The sharp- 
ness of the posterior ridge from the umbo varies much, as 
does the amount of inflation of the valves, forming, it seems 
to me, perfect gradations into cerinus. 
Unio cuneus Conrad. Corney Bayou. Rar 
Unio cornutus Barnes. Caddo Lake, ut Lake, Bayou 
Pierre. Not very abundant, and very constant in its charac- 
ters. 
Unio castaneus Lea. Corney Bayou, Cypress Bayou, Dor- 
cheat Bayou. It is very abundant in these streams. The 
specimens from the two first are very small and somewhat com- 
pressed ; those from Dorcheat are the largest that I have ever 
