44 
Aug. F. Foerste 
or Southgate division of the Eden, associated with Batostoma 
jamesi, Callopora nodulosa, Coeloclema alternatum, and Dekayella 
ulrichi. 
Strophomena hallie is known at present only from the Eden of 
Kentucky, Ohio, and Indiana. If the Eden be correlated with 
the Frankfort shales of New York and the Sevier shale of the south- 
ern Appalachians, then the absence of any representatives of 
Strophomena hallie in these strata is significant. In the equiva- 
lent strata along the northern parts of Lake Huron and thence 
along the southern shore of Georgian Bay to the vicinity of To- 
ronto, no species of Strophomena is known. The Eden is entirely 
absent in the northern part of the Mississippi Valley. From these 
data it seems probable that Strophomena hallie is a species of 
southern origin. This conclusion is favored also by the much 
greater abundance of Strophomena hallie in central Kentucky, 
and thence eastward as far as Alaysville, than farther northward 
and northwestward, in Ohio, Indiana, and the northwestern 
exposures of Kentucky. A similar conclusion might be reached 
also from the presence of Strophomena hallie in the southern fauna 
at the base of the Eden section as exposed in central Kentucky. 
This southern fauna includes Eridorthis nicklesi, Clitambonites 
rogersensis, Heteropora foerstei, a species of Hebertella, and other 
species not known in the contemporaneous strata farther north- 
ward, or but rarely found there. These lower strata, forming 
the Bogers Gap division of the Eden, present an assemblage of 
species so different from the lower or Economy member of the 
Eden that there is a tendency to classify them with the middle 
Eden. They appear, however, to indicate rather how far north- 
ward the southern type of Eden had progressed locally during the 
deposition of the earlier part of the Eden. 
Strophomena hallie belongs to the group of shells characterized 
by a weak delimitation of the muscular area of the pedicel valve, 
especially anteriorly. This area is not flabellate, nor is it extended 
anteriorly into a gap; its general form is roundish. The radiating 
striae, although not coarse, tend to be coarser than those of the 
Strophomena planumbona type of shells. Strophomena hallie is 
regarded as a precursor of Strophomena maysvillensis, a much 
more coarsely plicated species, ranging from the base of the Mount 
Hope to the upper parts of the Fairmount members of the Mays- 
ville. 
