184 ANNALS OF THE CARNEGIE MUSEUM. 
Kentucky River for A. minor (Lea) (Ortman, 1924, pp. 24, 42, and 
1925, p. 345) a Cumberlandian type. The Green River form is 
absolutely identical with it, but it is also identical with A. calceolus 
of the Ohio drainage. This removes this species from the list of the 
purely Cumberlandian shells. 
Micromya nebulosa (Conrad). I have considered this a Cumber- 
landian shell (/. c. 1924, pp. 30, 42, and 1925, p. 355). I now think, 
that this does not essentially differ from M. iris (Lea) of the upper 
Ohio, and it is even found in a form, impossible to distinguish, in the 
Lake-drainage (novt-eboract). On the other hand the ir7s-type is also 
found in the Cumberland, and occasionally in the Tennessee, and all 
this forces us to remove this whole association of forms from the 
Cumberlandian types. 
Dysnomia torulosa gubernaculum (Reeve). This hitherto has been 
known only from the upper Tennessee. But since it is only a form 
derived from D. torulosa, which is an Ohioan shell, it is not strange 
that it turns up again in Green River, having here the same relation 
to the main species. This cancels gubernaculum in the list of the 
Cumberlandian types. 
In this connection it is well to point out that a case similar to the 
last one has come to light in Micromya ortmanni. This has a certain 
similarity to the Cumberlandian M. vanuxemensis. It seems to me, 
however, that both vanuxemensis and ortmanni are derived from the 
lienosa-stock of the Gulf Coastal Plain, Mississippi Embayment, and 
lower Ohio region. They are parallel forms, originated independently 
of each other under similar conditions. The only difference from the 
case of Dysnomia torulosa gubernaculum is that in the latter the two 
forms cannot be distinguished, while M. vanuxemensis and ortmanni 
are easily told apart. 
The above considerations substantiate the conclusion, that there 
are no characteristic Cumberlandian types in Green River. There are 
no shells hitherto known to occur only in the Tennessee and Cumber- 
land’, which have extended their range into this system, without 
having reached other parts of the Ohio drainage. 
This seems to prove that there must have been at some time in 
the past a disconnection of the waters of Green River and of that system 
in which the Cumberland fauna originated. The present connection of 
8 Of course, we here disregard the fact that some of the Cumberlandian types 
turn up again in the Ozarks; and that others are found in the Alabama drainage. 
