Maryland Geological Survey ^11 



Orthoceras exile Grabau, 1899, BulL Buffalo Soc. Nat. Sci., vol. vi, p. 288, 



fig. 222 on p. 287. 

 Orthoceras exile Clarke, 1903, N. Y. State Mus., Bull. 65, p. 625. 

 Orthoceras exile Grabau and Shimer, 1910, N. Am. Index Fossils, vol. ii, 



p. 52, fig. 1252a. 



Description. — Shell straight, slender, regularly and gradually enlarging 

 from the apex; transverse section circular. Living chamber cylindrical, 

 large, length equal to more than three times the diameter at the last 

 septum; air-chambers numerous, increasing in depth toward the outer 

 chamber, varying from two or three mm. to five mm. in the length of 100 

 mm., or about thirty chambers. Septa smooth and thin; sutures straight 

 and horizontal ; siphuncle eccentric, distant from the nearest point on the 

 walls of the air-chambers about one-third the diameter of the tube. Test 

 and surface markings not observed; internal mold smooth, showing no 

 traces of the surface markings. This species differs from 0. constrictum 

 and 0. suhulntum in its eccentric siphuncle and more distant septa; while 

 the septa are comparatively more frequent than in 0. telamon and 0. 

 emaceratnm, and the siphuncle is smaller and less eccentric than in the 

 former. 



The Maryland specimens which are compared with this species are all 

 fragmentary and part of them greatly flattened by crushing, so that the 

 material scarcely admits of accurate specific identification. The depth 

 of the air-chambers, however, varies from 3^ to 4 mm. and the siphuncle 

 is eccentric, characters which agree with those of 0. exile. Prof. Hall 

 reported this species from Hamilton rocks at Cumberland, Maryland.^ 



Occurrence. — Eomney Formation, Hamilton Member. East bank 

 Evitts Creek below Wolfe Mill. 



Collection. — Maryland Geological Survey. 



Orthoceras telamon Hall (?) 

 Plate XL, Figs. 1-4 



Orthoceras telamon Hall, 1879, Pal. N. Y., vol. v, pt. ii, p. 291, pi. Ixxxv, figs. 



3, 4, 12. 

 Orthoceras telamon Grabau, 1899, Bull. Buffalo Soc. Nat. Sciences, vol. vi, 



p. 289, fig. 223 on p. 288. 

 Orthoceras telamon Clarke, 1903, N. Y. State Mus., BulL 65, p. 642. 



1 Pal. N. Y.. vol. v, pt. ii, p. 291. 



