14 
NAniLOIDEA. 
Orthoceras lamellosum. Hall. 
1846. Orthoceras lamellosum, Hall, Pal. of New York, vol, i. p. 312, 
pi. 1x3 xvi. ff. 2, a-e. 
1875. Orthoceras lamellosum, Xickolson, Pal. of Ontario, p. 36, f. 12, h. 
Sp. Char. Slender, very gradually tapering to an acute point; 
septa distant about 4 the diameter ; siphuncle slightly eccentric ; 
surface apparently lamellose or subimbricate. 
Remarlcs. Professor Hall states that “ this species is of frequent 
occurrence in the calcareous portions of the Hudson Eiver Group.” 
Horizon. Hudson Eiver Pormation ( = Bala Limestone Group?). 
Locality. Western Ontario, Canada. 
Eepresented by two fairly good specimens. 
Orthoceras Duseri, Hah & Whitfield. 
1875. Orthoceras Biiseri, Hall & Whitfield, Geol. Surv. ofOhio, vol. ii. 
pt. 2, Palffiont. p. 97, pi. iii. ff. 2-4. 
? 1881. Orthoceras Fosteri, MiUer, Journ. Cincinnati Soc. Nat. Hist, 
vol. iv. No. 4, p. 319, pi. viii. £E. 7, 7a. 
1886. Orthoceras Duseri, J. F. James, Joum. Cincinnati Soc. Nat. 
Hist. vol. viii. No. 4, p. 241. 
Sp. Char. Section circular or elliptical, (? by pressure) enlarging 
rather rapidly at the rate of about 1 in 6. Septa closely approximate, 
but increasing gradually in distance with the growth of the shell, 
so that they are about 1 line apart where the shell has a diameter 
of 5 lines, and about IJ line where the diameter has increased to 
10 fines, and so on. “ Siphuncle eccentric, situated a little nearer 
to the centre than to the margin ; very small where it passes through 
the septa, but expanding within the chambers to about four times 
its diameter at the other point, and forming a flattened bead-like 
body within each chamber. Surface of the shell apparently smooth 
except that the edges of the septa are raised above the general level, 
in the form of narrow rings.” {H. IF.) 
Remarks. Messrs. Hall and AVhitfield describe the surface of the 
shell in 0. Duseri as having a finely reticulate or net-like character, 
‘ ‘ dividing the surface into small rhombic figures of microscopic 
dimensions,” &c. I think these appearances are due to an encrusting 
Monti cufiporoid Coral, of which I find traces adhering to the speci- 
men in the National Collection. 
Horizon. Cincinnati Group (=; Lower and Middle Bala?). 
Locality. Ciucinnati, Ohio. 
Eepresented by one imperfect example. 
