291 



Orthoceras sp. (Fig. 225B.) (Pal, X. Y.. Vol. \ '.. PI. 

 LXXXVII.) 



A macerated specimen of an undetermined species, from 

 Eighteen Mile Creek, Lake Erie Shore, showing the effect of 

 compression in the soft shales. 



The figure is reproduced from Hall. 



Orthoceras constrictum. Vanuxem. i Pig. 225C. ) 

 (Pal. N. Y., Vol. Y., Pt. II., p. 288 3 Pis. LXXXIV., 

 LXXXV. ) 



Distinguishing Characters.— Straight, regularly enlarging 

 shell, with apical angle six degrees ; circular transverse sec- 

 tion; living chamber broadly constricted anterior to the 

 middle; numerous regular air chambers with a depth of 

 from 2 to 3 mm.; smooth, thin septa; central siphnncle. 

 Distinguished from 0. exile by its more closely placed septa, 

 and its central siphuncle. 



Found in the Hamilton group of Eighteen Mile Creek. 

 (Coll. Am. Mus. Nat. Hist. New York.) 



Genus GOMPHOCERAS. Sowerby. 



[Ett. : Oomphos, club ; keras, horn. ] 

 (1839: Murch. Sil. Syst,, p. 620.) 



Shell straight or curved, pear-shaped, greatest diameter 

 in front of the middle; cross-section circular. Mouth con- 

 tracted, opening by a T-shaped aperture. Siphuncle cen- 

 tral or excentric, sub-cylindrical or expanding between the 

 septa* (moniliform). 



Gomphoceras manes. Hall. (Fig. 226.) (Pal. N. Y.. 

 Vol. V., Pt. II., p. 339, PI. CXXIII. Supplement.) 



Distinguishing Characters.— Large size; fusiform out- 

 line; greatest gibbosity at last septum; regularly tapering 

 towards both ends; large aperture, with entire margins: 

 nearlv smooth surface. 



Found * * " in the dark Carbonaceous beds of the Gen- 

 esee slate, south of Alden, Erie County, N. Y." (Hall, 

 type.) 



