EL. W. Hilgard—Geology of Lower Louisiana. 81 
who attributes their origin to “ hydrothermal” or “ volcanic ” 
action. His descriptions are sufficiently faithful to show the 
general resemblance of their geological structure; so that after 
visiting the three middle members of the chain, viz: Cédte 
Blanche, Weeks’s Island, and Petite Anse, I have thought it 
viz: Belle Isle, the promontory west of Atchafalaya Bay, and 
Miller’s Island (or “ Orange Grove,”) overlooking the plains of 
e Vermilion. These elevations lie nearly ina straight line 
ing N.W. by W. from Belle Isle. 
Céte Blanche. 
calcareous or ferrugino-calcareous concretions along the strati- 
fication lines. Ata few points, these calcareous concretions 
resolve themselves into distinct fossils, representing the fresh- 
water genera Paludina, Melania, Unio, Anodonta and Cyclas, 
i an indifferent state of preservation, The entire visible pro- 
file is about 50 feet high ; the highest point of the island rises 
as high as 180 feet, but in its interior no exposures exist, so 
that the higher members of the series are not verifiable. _ 
Weeks’s Island. 
marsh. : 
Am. Jour. Scr.—Szconp Serres, Vou. XLVI, No. 139.—Jan., 1569. 
6 : 
