GASTROPODA. 1013 
Hormotoma.] 
utilized.* The third qualification lies in the comparatively obvious fact that the 
rather numerous species comprised in the genus constitute an evolutional series. 
That this is so can scarcely escape anyone who will take the trouble to compare 
critically the various forms which we refer here. A fourth and very important 
quality of the genus is its convenience in classification. The use of the term 
Hormotoma tells us at once that we are dealing with practically imperforate shells 
forming a high spire composed of numerous rounded or subangular whorls having 
simple surface sculpture and a subcentral flat or concave band terminating in a deep 
>shaped notch. These features furthermore are all readily apparent on all reason- 
ably well preserved specimens. 
The most natural position and true relations of Hormotoma appear to be with 
Plethospira, Ulrich, on the one side, and Turritospira, Ulrich, on the other. From 
the former it is distinguished by its higher spire, more numerous and slowly 
enlarging volutions and deeper apertural notch; from the latter chiefly by the 
central position of the band which, in that genus, lies considerably beneath the 
middle of the whorls. Twurritospira may not be as closely related as the great 
similarity of its shells leads one to suppose. Considering the position and relative 
prominence of the band and the external contour of the whorls in that genus, 
we see much to remind us of those low-spired and equally ancient genera 
Euconia and EKotomaria. Accordingly we are prepared to see it proved that 
Turritospira is nothing more nor less than a high-spired type of one or the other 
of those genera. 
In some of its forms Lophospira slightly resembles Hormotoma, but the more 
angular whorls and, especially, the convexity of the band in that genus renders 
confusion in this direction highly improbable. And yet, there is a possibility that 
some kind of relation exists between the two genera. [Evidence of such a condition 
is furnished by two species, one, a Calciferous form described by Billings as Murchi- 
sonia artemesia, the other, an Upper Silurian shell described by Lindstrém as M. 
attenuata Hisinger sp., which have all the characters of Hormotoma except the band 
which is convex as in Lophospira. We are in doubt as to what should be done with 
these geologically widely separated two species, but would advise that they be 
referred provisionally to Hormotoma and leave it to the future to determine whether 
"_ *Goniostropha might be retained as a subgenus under Hormotoma, Salter, or posstbly as a distinct generic designation 
for the Devonian group of species which we would otherwise refer to Hormotoma as the Desiderata section; providing that 
the slit-band in @hlert’s type, M. (Goniostropha) bachelieri Ronault sp., terminates in a short slit. That such aslit is present 
in the bacheliert we believe highly probable, and our investigations so far lead us to expect its presence in the majority, if 
not in all, of the Devonian shells agreeing otherwise strictly with Hormotoma. Still, in the absence of positive knowledge 
on the point, we do not consider ourselves justified in accepting Goniostropha for the group of shells in question. However 
the investigation of the species bachelieri may turn out, we are convinced that less than half of the twenty species referred 
to his subgenus by @hlert really belong there, With some of the species we are not sufficiently acquainted to pass judg- 
ment upon them. Of the others we would say that M. cingulata Hisinger, and M. moniliformis and M. obtusangula of Lind_ 
strém, are not at present distinguishable from Hormotoma; that M. cochleata Lindstrém, M. extenuata Conrad, M. angulata 
d@’Arch. and Vern., and M. (@.) chalmasi Ghlert, belong to various sections of Lophospira; and that M. micwla Hall, and 
M. larcomi McOoy, belong to an easily recognized and long-lived type which we propose to name Solenospira, 
