1893.] Mollusks of Louisiana. 959 
purple nacre remain constant, the variations being of essen- 
tially one type of structure. 
nio tuberculatus Lea. Corney Bayou, Dorcheat Bayou, 
Bayou Pierre, Cross Lake. It is rather abundant in the two 
first localities. Some of the specimens from Corney Bayou 
had the posterior portion very much elongated. Both the 
purple-nacred and white-nacred varieties were found. 
Unio gibbosus Barnes. Corney Bayou. A small, compressed 
variety was found in great abundance in this stream. 
Inio rotundatus Lamarck. Cross Lake, Bayou Pierre. This 
species is rather rare in Cross Lake, but, judging from the 
number sent me by Mr. Williamson from Bayou Pierre, it 
must be very abundant there. It is found abundantly in 
southern Louisiana. It appears that when northern Louisiana 
is reached, the northern extension of the species is being ap- 
proached. A specimen of this species was collected on the 
border of Cross Lake, September 26, 1891, supposed to be dead. 
It was laid upon my table to await a convenient opportunity 
for washing and putting away. On November 18, I tried to 
prize the valves open, but they would not yield. The animal 
was cut out, and its heart was seen to be still beating. The 
mussel had lived almost two months on my table, out of the 
water. 
MARGARITANA. 
Margaritana confragosa Say. Caddo Lake, Lake Bisteneau, 
Cross Lake, Corney Bayou, Bayou Pierre. The species is rare 
everywhere, but is most abundant in Caddo Lake, where I col- 
lected about one dozen specimens. 
Margaritana complanata Barnes. Corney Bayou. Rare. Out 
of a great many thousand specimens of Unionida from Corney, 
I obtained only two of this species. 
ANODONTA. 
Anodonta, tetragona Lea. Dorcheat and Corney Bayous. Not 
abundant. : 
Anodonta stewartiana Lea. Lake Bisteneau and in a pond 
near Jonesville, Texas. Rare. 
