788 THE PALEONTOLOGY OF MINNESOTA. 
([Orthoceras olorus. 
Formation and locality——In the Trenton horizon at Minneapolis (Lake Street bridge), Pleasant 
Grove, St. Paul, Cannon Falls and Fountain, Minuesota; in the Galena shales at Warsaw, Minnesota. 
The original specimens were from the lower and middle parts of the Trenton limestone at Middle- 
ville and elsewhere, New York. 
Museum Register, Nos. 350, 381. 
OrtTHOocERAS oLorus Hall, 1877. 
PLATE LY, FIGS. 3 and 4. 
Orthoceras vertebrale HALL, 1847. Paleontology of New York, vol. i, p. 201, pl. xutt, figs. 5a-c. 
Orthoceras olorus HALL, 1877. In Miller’s American Paleozoic Fossils, p. 245. 
To this species are referred a few specimens with rather distant, narrow and 
elevated annulations, which are slightly undulating and are traversed by alternating 
elevated vertical striz and these crossed by extremely fine horizontal lines. None 
of the material is good and such characters as are retained by the specimens show 
no great dissimilarity from the original. The septum is moderately convex, the 
sipho subcentral and the sutures, in the only example where clearly shown, follow 
the annulations and lie in the bottom of the constrictions. The species has a general 
resemblance to Orthoceras perroti, but differs in its more distinct and stronger 
annulations. In one example there are nine annulations in a length of 45 mm.; in 
another, five ina length of 25mm. The diameter of the shell in both of these is 
about 30 mm. 
Formation and locality.—In the lower blue beds of the Trenton limestone, Mineral Point and Janes- 
ville, Wisconsin; St. Charles and Holden, Minnesota; Galena shales, at Wykoff, Minnesota. 
Museum Register, Nos, 252, 379, 8291, 8292. 
ORTHOCERAS TENUISTRIATUM Hall, 1847. 
PLATE LY, ries. 4 and 6. 
Endoceras proteiforme, var. tenwistriatum Hau, 1847. Paleontology of New York, vol. i, p. 209, 
pl. XLV, figs. la-b; pl. xLvU, figs. la—-b, 2a-c. 
Shell long, straight, gradually expanding. Sutures direct; septum regularly 
concave and very slightly oblique. Sipho subcentral, small. 
Surface of the shell without annulations or ridges; marked by fine, crowded 
horizontal lines, somewhat undulating or irregular, often running into one another, 
rounded on the summit and subimbricating, separated by low furrows and divided 
at irregular intervals by a furrow of more than average width. These horizontal 
lines and furrows are crossed by extremely fine vertical lines seen only under 
magnification. Thanks to incarceration in the siphonal cavity of Cameroceras, one 
example of this species shows the surface ornamentation in a highly satisfactory 
manner. It even retains a series of narrow vertical bands which do not in any way 
