36 
Aug, F, Foerste 
and Anderson counties, and here Strophomena vicina is most 
abundant, although it occurs at corresponding horizons also far- 
ther eastward. It reappears at the top of the Lexington lime- 
stone, in the Cornishville member, in Mercer and Boyle counties. 
Both the Cornishville member and the underlying Perry ville mem- 
ber thin out northeastward, so that their faunas may be regarded 
as of western or southwestern introduction, as far as this part 
of the evidence is concerned. 
In the Cornishville member, Stropho7nena vicina is associated 
with numerous specimens of Dinorthis ulrichi, and specimens of 
Dinorthis ulrichi occur also locally at the lower Strophomena 
wcma horizon, near the base of the Paris member. Both species 
probably entered the areas traversed by the Cincinnati geanti- 
cline from the same source The nearest relatives of Dinorthis 
ulrichi are Dinorthis meedsi and its variety germana, from the 
lower part of the Prosser in Minnesota, Iowa, and Wisconsin. 
Both in Kentucky and in Minnesota these species are associated 
with Hehertella frankfortensis, a very common species of the 
Paris and Cornishville members of Kentucky, and of the Bigby 
of Tennessee. Moreover, in Minnesota, Strophomena trentonensis, 
Hehertella frankfortensis, and Dinorthis meedsi-germana are asso- 
ciated in the Nematopora bed, although Strophomena trentonensis 
is listed chiefly from the Clitamhonites bed, at the base of the 
Trenton, and in the immediately underlying part of the Black 
River group. From these data it may be assumed that Stro- 
phomena vicina, Dinorthis ulrichi, and Hehertella frankfortensis 
entered Minnesota, Kentucky, and Tennessee from the same source 
and that this source lay west of the Cincinnati geanticline. 
The apparent absence of any relative of Strophomena vicina or of 
Dinorthis ulrichi at corresponding horizons within the area cov- 
ered by the Columbia folio, suggests a northwestern, rather than 
southwestern origin for these species, although it is acknowledged 
that the argument is based upon insufficient data. 
Of much more interest is the suggestion that, whatever the ori- 
gin of Strophomena vicina, it probably was different from that of 
Strophomena incurvata. Strophomena vicina belongs to the Stro- 
phomena planumhona type of shell, in which the striations are 
still fine, although usually coarser than in Strophomena incurvata, 
while the muscular area' of the pedicel valve is not flabellate but 
has the anterior prolongation or gap. This type of shell dis- 
