291 



Orthocerah yp. (Fig. 22oB.) (Pal. N. Y., Vol. V., PL 

 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 fignre is reprodnced from Hall. 



Orthoceras coxsTRicTrM. Yannxem. ( Fig. 225C. ) 

 (Pal. N. Y., Yol. Y., Pt. II., p. 288, lis. LXXXIY., 

 LXXXY.) 



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 chand)ers with a depth of 

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

 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. 



[Ety. : Gomphos, club; keras, horn.] 

 (1889: 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 ( monilif orm ) . 



Gomphoceras manes. Hall. (Fig. 226.) (Pal. X. Y., 

 Yol. Y., 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, Avith entire margins ; 

 nearly smooth surface. 



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

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



