CEPHALOPODA. 
315 
BAC TRITES, Sandberger. 1841. 
The genus Bactrites was founded by Dr. Guido Sandberger in 1841, and its 
principal characters indicated by him in Leonh. und Broun’s Jahrb., p. 240. 
In 1850 Drs. G. and F. Sandberger reproduced the definition of the genus, 
with descriptions and figures of three species: B. carinatus, B. gracilis , and B. 
subconicus, in their great work, Die Versteinerungen des Rheinischen Schiclitensy stems 
in Nassau; p. 124, pi. 11, 12, 17. 
Since its first publication the genus has been recognized by other naturalists 
in several countries of Europe, among whom are Prof. F. A. Bgemer, Dr. Giebel, 
Dr. Ferd. Rcemer, M. J. Barrande, Prof. Gustave Laube and others. 
Uutil the present time no notice of this genus has been published in 
America. The number of species described from all the palaeozoic countries is 
very limited, compared with the other' allied genera. Only thirteen species 
have been recognized. Two of these are from the Silurian of Bohemia and 
Russia. Eleven species have been described from the Devonian of the Rhenish 
Provinces and the Harz. In Bohemia, where Cephalopodous life reached its 
maximum development, only one species has been indicated; and this is very 
limited in its vertical distribution. Two forms have also been recognized in 
the Triassic. 
The species here described is from the Marcellus shales, at the base of the 
Hamilton group, and has only been observed among collections from a single 
locality. As a whole, the genus seems to be essentially a Devonian form, and 
very local and irregular in its vertical and geographical distribution. 
On account of the slight “ dorsal lobe” of the suture lines, over the insertion 
of' the siphuncle in the septa, these forms have been considered as belonging 
with the Goniatitidse. In well preserved specimens, where the septal margins 
are nearly entire, this bending of the sutures is very slight; and is not a proper 
sinus in the septa, but is apparently a sinus in the chamber walls, made by the 
exposure of the siphuncular tube. Many Gyroceras and Trociioceras show a 
similar sinus in the septal sutures, where the siphuncle is submarginal. The 
genus Orthoceras, as now constituted, admits of so great a range of variation 
