CEPHALOPODA. 
473 
Goniatites Oweni, var. parallela. 
PLATES LXXIII, FIGS. 1, 2; LXXIV, FIG. 10. 
Goniatites Owmi, var. paralltla, Hall. Thirteenth Rep. State Cab. Nat. Hist., p. 101, figs. 13, 14. 1860. 
“ “ “ “ “ Illustrations Devon. Fossils: Cephalopoda, pi. 73, figs. 1,2. 1876. 
The Goniatites Oweni, var. parallela, was indicated in the original description 
of the species. 
The form and general proportions of this variety are not materially different 
from the typical forms of the species, though the volutions are sometimes less 
rotund. The umbilicus is always smaller, and the inner volutions a little more 
covered. The sides of the dorsal lobe are quite parallel, and the extremities 
reach beyond the arch of the saddle in the next posterior septum. This gives 
an apparent continuity to the septa, and the ventrum is thus impressed with 
two parallel continuous grooves limiting the margins of the ventral lobes. 
This feature indicates a closer arrangement of the septa throughout—a feature 
usually quite perceptible on the lateral faces of the volutions. 
In addition to these characteristics the tube is often, or usually, distinctly 
constricted at somewhat regular intervals by shallow, transverse grooves, which 
affect the smallest specimens, but which become more conspicuous in older ones, 
as shown in figure 8 of plate 73. 
It is, however, by no means established that this constriction affects only 
the var. parallela, for it is sometimes seen in the younger and more rotund forms 
possessing the typical characteristics, while the septa are comparatively more 
distant, the impressed lines on the ventrum are not continuous, and the ventral 
lobe does not extend so far as the summit of the next posterior saddle. This 
is true in some well-preserved forms of younger individuals, and it may be 
a question whether the characters distinguishing the varietal form are not 
acquired in the progress of growth. 
The two varieties of form occur in the same locality and position and without 
marked difference in comparative numbers. 
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