Maryland Geological Survey 313 



Orthoceras emaceratum Hall (?) 

 Plate XL, Fig. 7 



Orthoceras emaceratum Hall, 1862, Fifteenth Rep. N. Y. State Cab. Nat. Hist., 



p. 170, pi. viii, fig. 7. 

 Orthoceras emaceratum Hall, 1879, Pal, N. Y., vol. v, pt. ii, p. 292, pi. xxxix, 



fig. 4; pi. Ixxxv, fig. 16. 

 Orthoceras emaceratum Grabau, 1899, Bull. Buffalo Soc. Nat. Sciences, vol. 



vi, p. 290, fig. 225 A on p. 289. 

 Orthoceras emaceratum Clarke, 1903, N. Y. State Mus., Bull. 65, p. 624. 



Description. — Shell straight, slender, gradually enlarging from the 

 apex; transverse section subcircular. Living-chamber not seen; air- 

 chambers regular, gradually increasing in depth toward the living- 

 chamber, varying from six to nine mm. in the length of eighty mm. 

 Septa and siphuncle unknown; sutures straight and horizontal. Test 

 not preserved, but some specimens show traces of transverse striae; in- 

 ternal mold smooth, with the sutures but little impressed. One frag- 

 ment, with twenty air-chambers, has a length of 125 mm., with a 

 diameter at the smaller end of ten mm. The distinguishing characters 

 are the depth of the chambers, compared with the diameter of the tube, 

 and tbe small apical angle. In its general aspect and association it is 

 similar to 0. aulax; but the marked surface ornaments on the latter 

 species, which are also shown on the internal mold, are characteristic. 



In the Maryland Collection is a single flattened internal impression 

 which probably belongs to this species. Five air-chambers and a portion 

 of the sixth are shown which vary in depth from 6 to 6^ mm. This 

 specimen was examined by Dr. Eudolph Ruedemann, who wrote as fol- 

 lows concerning it : " This is 0. emaceratum Hall, distinguished by its 

 small apical angle and great depth of the air-chambers." 



Occurrence. — Eomney Formation, Hamilton Member. W. Va. 

 side Potomac River 3 miles south of Cumberland. 



Collection. — Maryland Geological Survey. 



Orthoceras cf. aulax Hall 

 Plate XL, Fig. S 



Orthoceras aulax Hall, 1S79, Pal. N. Y., vol. v, pt. ii, p. 293, pi. Ixxxiv, fig. 18. 

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



289, fig. 224 on p. 288. 

 Orthoceras aulax Clarke, 1903, N. Y. State Mus., Bull. 65, p. 618. 



