THE 
AMERICAN GEOLOGIST 
Vol. IV. OCTOBER, 1889. No. 4 
THE SUBGENERIC GROUPS OF NATICOPSIS. 
By Charles R. Kf:yks. 
The described species of Naticida; from the American pala-o- 
zoic rocks number about three score. These have commonly 
been referred to the genera Natkopsis, Flatystoma and 
Strophostylus. The first of these three terms was proposed 
in 1844 by McCoy,' and included shells which had previously 
been assigned to the modern genus Natica. Seven species 
were enumerated under the new title ; but of the accompany- 
ing figures only two showed the apertural characters. In 
America the shells of this group were first recognized by Nor- 
wood and Pratten,' who described from the Coal Measures, 
Natica ventf'icosa. Shortly afterward several other forms 
were detected and placed under the same genus. It was then 
found that McCoy's generic term was applicable to the Ameri- 
can forms hitherto regarded as Xaiicce. And it has recent- 
ly been discovered that in addition to the species generally 
recognized as belonging to Xatlcopsis, the genus should also 
include several other forms now known under other generic 
titles. 
The species that have been referred to Naticopsis appear to 
'Syn. Carb. Foss. Irelaml, p. 33. 
2 Jour. Acad. Nat. Sci., Phila., 1855. 
