GASTEROPODA OF THE LOWER GREEN MARLS. ~ 159 
them identical, I have taken them as they are identified and labeled in the 
collection Acad. Nat. Sci. Phila., and partly from his descriptions. In his 
comparisons under A. ovoidea he says that species can be distinguished from 
this one by “the proportionate length of the mouth, and narrowness of the 
body whorl, and the acute upper edge of the whorl.” The proportional 
length of the mouth is nearly as given in his description, i. e., less in this 
one. The volutions are more acute also in that one, while the proportional 
diameter of the body volution of the two species is very nearly the same 
in both. The width of the aperture is also greater here than in A. ovoidea; 
in these respects they nearly agree with his statements. The author 
remarks that in this species (A. cretacea) there are two folds on the colum- 
ella,” the upper one heavy and rounded, lower or anterior one obsolete.” 
If the lower one is obsolete, which it certainly is in the specimen here used, 
which is one of the types, it can not exist; therefore there is only one, and 
not two as he describes. In the other species a similar error is made, as to 
the relative size of the folds as the anterior one is barely distinguishable 
on the specimen, which is also one of those used in the original description. 
Mr. Gabb also states that on one of the casts of this species ‘‘the colum- 
ellar edge of the body whorl” ‘is marked by acute angular striz, one 
branch extending directly upwards on the outside of the whorls [inside of 
the shell], and soon becomes obsolete; the other branch runs into the 
columellar cavity.” This feature I can not understand, as the specimen is 
not before me, but I think that by some accident the description in this 
connection has become mutilated in the printer’s hands, and has escaped 
notice in proof-reading. In remarks below the description he states that 
from a cast of the surface he believes the exterior to be smooth. As it 
appears that I have not seen all the specimens used by the author, I have 
retained the name of the species and its identity, thinking it probably may 
be satisfactorily identified at some future time. 
Formation and locality: In the Lower Green Marl at Crosswicks, New 
Jersey. Collection Acad. Nat. Sci., Phila. 
