CEPHALOPODA. 
457 
This species is distinguished among others here described, by its wide 
umbilicus and gradually enlarging volutions, and in its flattened condition, 
by the fine, even, thread-like strim. The species was originally founded 
upon specimens like figures 10 and 11 of plate 70, in which the septate char¬ 
acter is usually very obscure, and often not all preserved, the general form 
and surface-markings being all that remain. The specimen figure 8, plate 70, 
is a cast of the interior, from which all remains of the external shell have been 
removed. The volutions are somewhat rotund. 
The form described as Clymenia Erato=Goniatites Erato is probably only 
a variety of G. complanatus. The specimens are larger than G. complwnatus 
in its usual condition, and the outer volution embraces somewhat more of 
the inner one; but with these exceptions they are too nearly similar to be 
separated, especially as no complete comparison can be made between the septa 
in the two forms. 
Among a considerable number of specimens, preserving the general form and 
proportions of figures 10 and 11, of plate 70, but little difference has been 
observed. The specimen figure 12 of plate 71 has a much greater diameter, 
and the proportional distance of the septa is greater than in any previously 
recognized form of G. complanatus. It is readily distinguished from G. sinuosus 
by the direction of the septa, though the general form of the shell and surface- 
markings are similar. 
Formations and localities. In the green shales of the Portage group, at Cash- 
aqua creek, in Livingston county, N. Y.; in the lower beds of the same forma¬ 
tion, on the east side of Cayuga lake; and in some concretionary layers in the 
upper part of the Hamilton group, on the shore of Lake Erie. 
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