Strophomena and Other Fossils 
121 
Hebertella insculpta at the Dinorthis carleyi horizon fixes the 
position of the latter. 
Leptaena richmondensis occurs in the Waynesville member also 
at Dismukes,4 miles north of Gallatin, in Tennessee. The species 
in the Fern vale member, in the Tennessee River Valley of west- 
ern Tennessee, in the Mississippi River Valley, and westward, is 
Leptaena unicosta, although Leptaena rhomhoidalis is listed from 
the Orchard Creek shales, in Calhoun county, Illinois, and from 
the Maquoketa of Iowa. 
In determining the source of Leptaena richmondensis, geograph- 
ically, it should be noted that it is associated in the Arnheim with 
Dinorthis carleyi and Rhynchotrema dentata, and apparently was 
brought in from the same source as that which furnished these 
species, arriving a relatively short time before the latter. Again, 
in the Waynesville member, Leptaena richmondensis makes its 
appearance before Dinorthis carleyi, the latter coming in at the 
lower Hebertella insculpta horizon, at the base of the upper or 
Blanchester division. Rhynchotrema dentata is seen farther up 
in the Blanchester division. Strophomena concordensis comes in 
at the close of the Arnheim, a considerable distance above Leptaena 
richmondensis, Dinorthis carleyi, and Rhynchotrema dentata. The 
corresponding species, Strophomena nutans, comes in 12 feet 
above the base of the Blanchester division, a considerable time 
later than the reintroduction of Leptaena richmondensis and Di- 
northis carleyi, but before the recurrence of Rhynchotrema den- 
tata. Since none of these species occur in the Mississippi Valley, 
they do not appear to have entered Cincinnatian areas from the 
west. Since Leptaena richmondensis, Dinorthis carleyi, and Rhyn- 
chotrema dentata are unknown in the long stretch from Drum- 
mond Island to New York State, they do not appear to have 
come in from the north; Rhynchotrema neenah, from Wisconsin 
and Illinois, is not sufficiently similar to Rhynchotrema dentata 
to indicate the origin of this species from the northwest. Con- 
nection with the St. Lawrence Valley and the east appears to 
be shut off by shaly and sandy Richmond deposits, practically 
unfossiliferous. This leaves chiefly a southern origin for that 
part of the Arnheim fauna here under discussion, notwithstand- 
ing the fact that the nearest relative to Dinorthis carleyi is Di- 
northis retrorsa, of Wales. 
