OF THE UNITED STATES. 39 
5. A. Conradi. (S.G.M.) pl. 16, fig. 1, 2, 3, and 
pl. 19, fig. 4. 
Specific character. Much compressed; one complete volu- 
tion and part of a second, the smaller being received into and 
concealed by the larger: five or six rows of tubercles on each 
side, the outer ones terminating at the peripheral margin, the 
inner ones at the internal margin of the whorl; tubercles 
united by sub-angular, slightly curved costa. Periphery sub- 
convex, and marked with three or four delicate, longitudinal 
lines. Septz innumerable, extremely tortuous and intricate. 
Largest diameter nearly two inches. Thickness half an inch. 
Pligxvi. fig. ati. 
I dedicate this species, the most beautiful fossil 
hitherto found in this formation, to its discoverer, my 
estimable friend T. A. Conrad, Esq. Mr. C. found it 
abundantly at Prairie Bluff, Alabama, in the older cre- 
taceous deposits. So variable, however, are its forms 
_ that I was at first disposed to consider myself in _posses- 
sion of three distinct species, which however, upon a 
comparison of upwards of fifty individuals, appear to 
have their essential characters, in common. The most 
remarkable of these varieties are the following. 
Variety 4. Pl. xvi. fig. ib. 
More ventricose, outer tubercles larger, inner ones almost 
obsolete: costz more distant, and larger. I had proposed for 
this fossil the name of A. gulosus, which will serve should it 
not prove identical with the former. 
Variety B. Pi. xvi. fig. i. 
Ventricose ; coste and tubercles remarkably distinct. This 
shell at first sight resembles an Argonauta, but itis a true Am- 
