770 THE PALEONTOLOGY OF MINNESOTA. 
[Nanno aulema. 
Nanno AULEMA, Sp. nov. 
PLATE XLVII, FIGS. 4—11. 
The material which represents this interesting type of cephalopod structure 
was collected by Messrs. E. O. Ulrich, Charles Schuchert and the late W. H. Scofield, 
from various localities in the Trenton series of Minnesota. _No similar forms have 
heretofore been found in the American faunas, and their novel character was 
recognized and studied by the first two of these gentlemen. Like bodies had, 
however, been found and described by Gerard Holm,* derived from the lower Silu- 
rian of Oeland and Esthland, and in the drift boulders about Eberswalde; they were 
referred by him to the genus Hndoceras, under the designation, EH. belemnitiforme 
Holm, but we feel guilty of no temerity in regarding them as representatives of a 
distinct type of structure. 
Our description is based essentially upon the American fossils, though supple- 
mented by comparisons with the European species. 
The usual form which these bodies assume is somewhat that of a small Belem- 
nites. The apical and posterior portion has a rounded, evenly tapering surface, 
which would give it the form of a true cone were not one side, when the body is 
viewed laterally, quite oblique, while the other is nearly vertical. Thus viewed the 
shells are asymmetrical laterally, but as seen from the dorsal and ventral sides they 
are bisymmetrical. After the conical expansion has extended for about one-half the 
length of the body, there is a rather abrupt contraction on the oblique side and the 
shell becomes more circular and much smaller in cross-section. Thus toward the 
upper extremity of the shell a cylindrical tube is formed. 
The normal position, however, of the conical posterior portion is such that the 
straight and the oblique side converge at the same angle; this diverts the cylindrical 
or upper portion of the body to one side. 
These peculiar bodies are siphones; that represented in figure 10 shows the 
oblique impressions left by the septa upon its surface, and figure 6 affords a concep- 
tion of the relations of these siphones to the septate part of the shell. In the latter 
is seen the central and symmetrical position of the apical cone with reference to the 
entire shell, its abrupt contraction and the deflection of the cylindrical portion of 
the sipho to one side. At the point where the contraction of the sipho begins, its 
diameter is that of the shell, and from the apex to this point there is no trace of 
septa. With the appearance of the septa begins the contraction of the sipho. That 
the septa did not completely encircle the sipho beyond the diameter of the 
siphonal funnels is shown by several of the specimens which present a smooth 
surface on the dorsal or outer side, the marks of the septa being there 
*Ueber die innere Organization einiger silurischer Cephalopoden; Dames und Kayser’s Paliiontologische Abhand- 
lungen, Bnd. III, Heft 1, pp. 4—9, pl. i, 1885. 
