962 THE PALEONTOLOGY OF MINNESOTA. 
[Lophospira. 
or greater differences in the hight of the spire are to be observed in the Perangulata 
section. Beginning with forms like L. ampla Ulrich and L. multigruma Miller, in 
which the apical angle varies from 70 to more than 90 degrees, we pass by numerous 
and easy gradations to L. bowdeni Safford, in which the angle is sometimes as narrow 
as 25 degrees. While the hight of the spire only rarely deserves to be counted among 
the generic characters, we believe it is, within reasonable limits, usually an excellent 
specific character. 
Concerning the systematic position of the genus, we may say with considerable 
confidence that it is the oldest of the many types strictly belonging to the family 
Pleurotomariide. We say this not so much because the genus goes far back in 
geological time, for, according to known facts, several other types are equally 
ancient, but because it shares characters with types belonging to other families 
which, like the Plewrotomariide, originated somewhere in the interval between the 
Calciferous and the Upper Cambrian. Thus the simplicity of the band and apertural 
notch allies the genus with the Euomphalide. A striking resemblance, indicating, 
we believe, also close relationship, obtains between certain species of Trochonema 
and Lophospira notabilis, L. knoxvillensis and L. trochonemoides. This relation of 
Trochonema to the notched pleurotomarian and euomphalid genera is shown not 
only by the species of Lophospira just mentioned, but is indicated quite as strongly 
by such undeniable Trochonemas as 7. retrorsa and T’. bellula. The latter have an 
apertural notch at the end of the supra-peripheral angle, causing the lines of growth 
to curve backward toward the angle from both above and below. Only one feature 
remains to distinguish the Trochonemoides section of Lophospira from T. retrorsa and 
its allies, and that is, that while the Lophospiras have a distinct band, the Trochon- 
emas have none, the lines of growth curving backward to and then over the angle 
without interruption in the latter. 
Lophospira is divisible into four sections, and two of these into several subsections 
as follows: 
A. Perangulata section:—Apertural notch >shaped, deep and wide, the lines of 
growth sweeping backward strongly from both above and below to the peripheral 
band. 
1. Perangulata subsection:—Shells not very high, whorls five to eight, strongly 
angular. Species:, L. perangulata Hall, L. sorocula Billings sp., L. modesta Billings 
sp., L. medialis U. and §., L. decursa Ulr., L. pulchella U. and 8., L. saffordi Ulr., 
L. abnormis Ulr., L. centralis Ulr., L. oweni U. and §., L. ampla Ulr., L. peracuta U. and 
S., LZ. elevata U. and.8., L. multigruma Miller sp., L. tropidophora Meek sp., L. swmner- 
