White on later Cretaceo^is deposits in Iowa. 225; 
ately prominent; posterior canal absent, but there is instead, a 
moderately broad notch at the junction of the posterior margin 
of the wing with the spire. The lower lobe of the wing is 
prominent, thickened, and rounded at the outer end; the falci- 
form process long, pointed and curved outward and backwai^d. 
The general shape and size of the shell is indicated by the ac- 
companying figure. 
The shell, in general aspect and in many of its details, is closely 
like Lisfodesthes nnptialis White, from the Cretaceous of Ari- 
zona. It has all the characteristics upon which the genus Lis- 
podesthes^ was proposed except the posterior canal, which in 
the type species is grooved out of the callus covering the spire, 
and which extends nearly to its apex. In this species however 
there is no such groove, but its other characteristics agree so 
closely with those of Llspodesthes that I refer this form to 
that genus, at least provisionally. The specific name is given 
in honor of Prof. Haworth who brought these fossils to my 
notice. 
In my former discussions of the Cretaceous deposits within 
the state of Iowa I have been disposed to treat them all as be- 
longing to the "Earlier Cretaceous" of Meek and Hayden; that 
is, as being older than the Fort Pierre and Fox Hills groups.. 
It is true that Mr. St. John regarded certain of the fish remains 
which were found associated with Cretaceous mollusca in the 
drift of Howard county as indicating a very late epoch of the 
Cretaceous, although he was not able to identify any of them 
with published species.^ 
While the value of the evidence furnished by the type char- 
acters of those fish remains was not overlooked, the lack of 
specific identification of any of them with forms whose strati- 
graphical position was known left the question as to whether 
they were of earlier or later Cretaceous age open to at least 
reasonable doubt Because of this, and of the fact that the fos- 
sil mollusca which were associated with those fish remains 
seemed to be, in part at least, specifically identical with forms 
w^hich characterize certain of the earlier Cretaceous strata in 
1 For the original generic diagnosis see U. S. Geog. Surv. (Wheeler's). 
West of the looth Meridian, vol. iv, p. 191. 
^ See article before cited, Proc. A. A. A. S. vol. xxi, p. 188. 
