Maryland Geological Survey 693 



Occurrence. — Jennings Formation, Genesee Member. Williams 

 Eoad near Cumberland. 



Collection. — Maryland Geological Survey. 



Suborder MESOCAMPYLI 

 Family PREMORDIALIDAE 



Genus MANTICOCERAS Hyatt 



Manticoceras patersoni (Hall) 

 Plate LXXII, Figs. 1-3 



Goniatites patersoni Hall, 1860, 13th Rept. N. Y. State Cab. Nat. Hist., p. 



99, figs. 9, 10. 

 Ooniatites patersoni Hall, 1875, 27th Rept. N. Y. State Cab. Nat Hist., 



p. 136. 

 Goniatites patersoni Hall, 1879, Pal. N. Y., vol. v, pt. ii, p. 464, pi. Ixxii, 



figs. 1-5; pi. Ixxiv, fig. 15. 

 Manticoceras patersoni Clarke, 1907, Rept. N. Y. State Geol. for 1S96, p. 45, 



pi. 1, figs. 1-12; pi. ii, figs. 1-4, 6; pi. iv, figs. 14-18. 



Description. — " Shell large, discoid ; the thickness of the disc equal 

 to a little more than one-third the lateral diameter of the shell in young 

 and medium-sized specimens. Volutions about four, the outer ones em- 

 bracing the inner to the depth of one-half or more of their dorso-ventral 

 diameter. Umbilicus of moderate width, exposing all the inner volutions. 

 Transverse section somewhat semielliptical, Avith tlie lateral faces convex 

 near the base, slightly concave beyond the middle of the width, and ab- 

 ruptly rounded at the apex or periphery. The base is deeply indented by 

 the preceding volution, and subauriculate at the baso-lateral angles. The 

 enlargement of the volutions is very gradual in the young state, and more 

 rapidly increasing as the shell advances in age. From the third to the 

 fourth volution the increase is from a diameter of fifteen mm. to thirty- 

 one mm. in a single turn. Chamber of habitation very large, in one 

 specimen occupying more than half a volution ; its full extent not known ; 

 its capacity is at least twice as great as all the chambered portion of the 

 shell. Aperture elongate semielliptical, narrowing toward the anterior 

 margin, which is subacutely rounded. Base deeply indented by the pre- 

 ceding volution, and, inferring from the form, it is subauriculate at the 



