AMERICAN PALEOZOIC CEPHALOPODS 
219 
species are relatively long, and the siphuncle is only moderately 
excentric. 
It is evident that the type of Orthoceras, if this genus is to be 
accredited to Breynius, must be some species which could have 
been carried southward by glacial action to the vicinity of Dan- 
zig. If any true Orthoceroid is known which could have been 
the species figured by Breynius, it is desirable that attention be 
called to this fact. 
In this connection it might be of interest to note that the 
genus Lituites was defined by Breynius in the same work in which 
he defined Orthoceras. In neither case was a binomial nomencla- 
ture used, and it is doubtful whether either genus, under these 
circumstances, should be ascribed to Breynius. 
The species figured by Breynius is cited by Schlotheim in his 
description of Orthoceras regulare, evidently in the belief that 
the two were identical. 
However, it is evident from his citations of figures of ortho- 
ceracones published by Bose, Knorr, and Breynius, that he in- 
cluded several species under this name, and that the species 
figured by Breynius can not be considered the type of regulare. 
Hyatt restricted the term Orthoceras to forms with smooth 
shell, and stated"'^ that he had met but two species in North 
America, though doubtless others may exist. In the Zittel- 
Eastman Text-book of Paleontology he figured two species under 
Orthoceras, namely intermedium Marklin from the Silurian of 
Gotland, and michelini Barrande from the Silurian of Bohemia. 
Of these two species, the first differs from typical Orthoceras in 
the greater number of its camerae (about 8 in a length equal to 
the diameter of the conch), and in the distinct, though slight, 
enlargement of the siphuncle within the camerae. The second 
species, however, is closely similar to typical Orthoceras in the 
elongation of its camerae and in the tubular form of the segments 
of its siphuncle. Until the exact status of the species figured by 
Breynius can be determined, Orthoceras michelini Barrande may 
be accepted as the type of Orthoceras as restricted by Hyatt. 
Typical Orthoceras occurs chiefly in the Silurian, but similar 
specimens apparently occur also in the Richmond formation, in 
the upper part of the Ordovician. A description of the species 
occurring in the Richmond at Clarksville, Ohio, follows : 
** Hyatt, A., Genera of fossil cephalopods; Proc. Boston Soc. Nat. Hist., 
vol. 22, p. 275, 1883. 
