114 
Tin . I merican Geologist. 
August, l^na 
The specimen is briefly described. It consists of tin- first 
or apical chamber of the shell, to which the protoconch is at- 
tached. The upper end of the specimen shows the first sep- 
tum (not counting the "apical plate" .separating the proto- 
conch from the first chamber) to be circular and with a central 
sipho. The lateral walls of the first chamber taper rapidly to 
the plane of conjunction with the protoconch and its depth is 
about one-half that of the latter. 
The protoconch itself is semiovoid in shape, and when com- 
pared with those of Orthoceras previously described or fig- 
ured, is of very large size. It shows no indication of shrink- 
ing or other irregularity and its distal extremity is perfectly 
smooth. 
The length of the entire specimen is .85mm. ; that of the 
protoconch, .60 mm., and the diameter of the first septum, 1 
mm. 
As this specimen was found by itself in no immediate asso- 
ciation with Orthoceras, the great size of the protoconch led 
at first to some doubt as to its correct generic relations. 
Although specimens of Orthoceras.&re not uncommon at this 
horizon, Bactrites is equally plentiful,* and the examples of 
both in my possession, in condition of preservation, leave lit- 
tle to be desired for the study eft developmental phases. The 
critical distinction between the protoconch in question and 
that of Bactrites is one of some delicacy and is, namely, the 
position of the sipho upon the first septum. Branco has 
*The usual species of Bactrites occurring .in the Styliola layer and, 
more abundantly, with the recurrence of the Intumescens-fauna in the 
"lower Portage," is probably the same fossil to which was originally 
given the name Orthoceras acicuhim, later called Coleolus aciculum. 
The usual mode of retention of this, as well as of the associated fossils 
distributed through the shales, does not often permit satisfactory de- 
termination of generic characters. 
