6 [355] A. Winchell on supposed New Cephalopods. 
Orthoceras robustum, n. sp.* 
A septate fragment of this species has such a curvature that 
the individual must have been 3*4 in diameter. Amougst other 
fragments of the last chamber of the shell, one is so large as to 
imply a diameter of 4*6. The septa appear to be transverse, 
separated from each other *31, where the diameter is 3*4, giving 
a ratio of 11. In another specimen this ratio is T5 : *98=6-54. 
Ho surface markings are indicated upon the casts. Siphon not 
seen. 
Localities. Marshall, Moscow and Hanover in Jackson county. 
This species has the size and general appearance of 0. gigan - 
teum Sow. (de Kon., op. cifc., 510, pi. xliv, 2; xiv, 3; xlvi, o, b ; 
xlvii, 1), but differs, as far as observed, in having the septa sep¬ 
arated by one-sixth to one-eleventh of their diameter, instead of 
one-third. It differs from 0. crassum F. Rom. (Sandberger, 
“ Verstein erun gen,” p. 164, Taf. xix, fig. 1) by a much greater 
approximation of septa; and this reason, as well as its very 
great size, has induced me to separate it from 0 . Indianense. 
Orthoceras vittatum. ? 
Sandberger (Verstein., 165 ; Taf. xx, 9). 
Shell very gradually tapering; transverse section circular; 
ratio of the depth of the chambers to their diameter *09: *22= 
2*56; ratio of concavity of septa to their diameter *07: *22=3*14. 
Siphon apparently slightly excentric. Surface (of cast) marked 
by delicate encircling bands, separated by rather sharp, fine 
grooves; four of these bands correspond to each chamber. 
There are also very feeble indications of striae covering the bands. 
Locality. In the Marshall sandstone at Battle Creek or Holland. 
The single specimen in my possession differs from Sandberger’s 
description only in the words “ taeniis transversalibus paullo ob- 
liquis .” It differs from 0. bicingulatum Sandberger (Verstein., 
162, Taf. xvii, 3) in the transverse direction of the rings, and 
the perfectly circular section. 
Orthoceras arcuatellum. ? 
Sandb. (Verstein, 166; Taf. xix, 2). 
Shell tapering to an angle of 12°; nearly smooth externally, 
with faint, encircling, unequal, irregularly sinuous striae; section 
circular; septa transverse, with a convexity equal to one-sixth 
or one-seventh their diameter; siphon central. (?) 
Locality. In the Marshall sandstone at Marshall. 
The general characters of this shell present a good agreement 
with the species to which I have doubtfully referred it; but it 
is easy to point out differences. Our shell has a much less rapid 
taper, and the encircling striae are much finer, more unequal, 
and not regularly reflexed on the anterior and posterior sides; 
moreover, no observations have yet been made on the depth of 
