Foerste.] 
282 
[May 1, 
thought to be a living chamber. The siphon of this form is not 
known with absolute certainty, although it is undoubtedly central 
or subcentral. 
Associated with this specimen are others which seem to belong 
to the same species. One of these specimens is 70 mm. long, having 
a diameter of 26.2 mm. at the smaller extremity and of 30 mm. at 
the larger end. It seems to have been a living chamber. The surface 
of the inner layer of the shell is finety striated transversely, about 
sixteen striae occupying a length of 2 mm. This specimen, however, 
differs from the typical forms of this species in having more strongly 
concave septa, these forming an arc of 128°. The stronger con- 
cavity is no doubt chiefly due to the smaller diameter of the circle 
through which it passes, owing to the smaller size of the specimen. 
Another specimen in the same piece of limestone as the type, hav- 
ing a diameter of 27 mm., with three chambers in a length of 17 
mm., also having septa forming an arc of 128,° shows the siphon. 
As far as may be judged from the specimen, the siphon is cylindri- 
cal, scarcely suffering any contraction at the septa, and presents 
an almost uniform diameter of 2.8 mm. for the three chambers in 
which it is exposed. Since we do not hesitate to associate these 
specimens with the t}^pe, this siphon is considered characteristic 
for the species. 
This form differs from Ortlioceras rigidum , Hall, originally de- 
scribed from the Lower Helderberg of New York, but recently also 
identified by Newell in the Upper Niagara of Indiana, by the smaller 
apical angle of the Ohio form, and the correspondingly smaller in- 
crease of the distance between the septa, with age, as compared 
with the 0. rigidum. Although readily distinguished from 0. rigi- 
dum , , the Ohio species is probably a closely related form. A 
knowledge of the siphon of the New York specimens is necessary 
to determine how close this relationship might be. 
Orthoceras (Cycloceras) annulatum, Sowerby. 
(PLATE VIII, FIG. 5.) 
A single specimen from Brown’s Quarry, near New Carlisle, O., 
not very well preserved, is very similar to specimens from the Clin- 
ton of New York usually referred to this species. It is quite strong- 
ly annulated transversely, there being nine annulations in a length 
of 43 mm. ; the annulations are scarcely .7 mm. high, and are sep- 
