1024 THE PALEONTOLOGY OF MINNESOTA. 
[Euomphalide. 
whorls, rounded or obtusely angular upon the upper side, the angle marking the 
bottom of a broad sinus in the lip; the first departure from this type consisted in the 
loosening and straightening of the last whorl (Hecyliomphalus, or as Whitfield would 
have it, Caularops canadensis Bill. sp.); next all the volutions became disjoined as in 
Ec. intortus and the later Ke. undulatus. We have no evidence to show that one or 
the other of these stages was not strictly maintained as a specific peculiarity by 
each of the early forms—it certainly was so with the Trenton species—but, accord- 
ing to Lindstrém, the whorls in his /. gotlandicus vary from closely coiled to perfectly 
evolute. All these species have a broad sinus in the upper lip and, so far as traced, 
we have found no evidence to show that the later (Devonian and Carboniferous) 
shells commonly referred to Straparollus (i. e. eaomphaloid shells having rounded 
whorls and nearly or quite straight transverse lines of growth) were developed from 
them. On the contrary Straparollus or Straparollus-like shells seem to us to have 
been evolved probably at several successive times from true Euomphali. Still, we 
are not prepared to say that some of them may not have been derived from the 
Lower Silurian species which Billings called Straparollina. However, though with 
nothing but Billings’ figures to base our judgment upon, we are strongly inclined to 
regard Straparollina as closely related to Holopea and consequently as widely distinct 
from the Euomphalide. 
In our opinion, therefore, Hecyliomphalus, as this genus is defined and used by 
most American authors, deserves recognition as a well-marked and limited generic 
group, principally because it represents a distinct line of development. Phanerotinus 
Sowerby, which is similar in habit and sometimes considered as. synonynious, is 
founded upon evolute Straparollus-Kuomphali of the Devonian and Carboniferous 
rocks. As now used the genus is not a natural group, but it may well be retained, 
provisionally at least, as a designation of convenience for those Euomphali having 
rounded and more or less widely disjoined volutions and no apertural sinus. In 
America only three species fulfill these requirements, viz.: P. parodoxus Winchell 
(Burlington group), and P. eboracensis (Hamilton group), and P. laxus (Corniferous 
group) of Hall. The second is peculiar because its shell attaches to itself foreign 
objects. Eecyliomphalus undulatus Hall had a similar habit, and its frequent 
occurrence in several European Devonian Euomphalide has been observed by 
Deslongchamps, Koken and others, and quite recently has led Kayser to propose the 
new generic term Philoxene (Zeitschr. d. deutsch.’geol. Gesellsch., Jahrg. 1889.) 
This peculiar feature reminds one of the recent genus Phorus, but we agree fully 
with Hall and Koken in attaching very little significance to its presence in these 
otherwise clearly Euomphaloid shells. 
As far as we can go back in geological history, the developmental line of 
