507 



Orth. 



Orthis acuminata, Billings. Can. Nat. Geol. Vol. 4, 1859. 



)/ 1\ 59 a Geol. Can. 1863, p. 130, figs. 59 a. ventral 



"^0^^ b rj valve ; 5, side view. Chazy limestone^ 



Orthis acutiloba, Ringueberg. Proc. Acad. Nat. Sci. Phila- 



V^ 



im 



5c. 

 PhllacU, \ 



Orthis aequivalvis. 



5 



Riii^ufi 5 ex. 5-b 



1888, part 2, p. 134, pi. 7, fig. 5, 5 a^ h, c, belonging to the 

 group of 0, iiloba. Lin. (See outline of this as fig. 6) ; and 0. 

 varica^ Con. ; but has a deeper sinus, and a hinge line only 

 half as long. Only two perfect ones yet found ; but a sinele 

 valve is sometimes found in the middle and lower divisions of 

 the Niagara shale at Lockport, N. Y. ( 0. hiloha seems absent 

 here.) — Vh, 



Hall. Pal. N. Y. Vol. 1, 1847, Tren- 

 '^0. ton. Emmons, Am. Geol. I, 

 ii, 1855, 196, pi. 9, fig. 6 a, J, c. 

 Shell symmetrica] ; more than 

 thirty folds, forking once or 

 twice. — Trenton formation, lie, 

 Orthis bellarugosa. Conrad, Proc. Acad. Nat. Sci. Phila. 



Vol. 1, 1843, Trenton. 

 Emmons, A. G. I. ii, 1855, 

 197, pi. 9, figs. 3 a, J, c, d; 

 small shell ; back valve 

 with a narrow groove in 

 the middle; folds numerous, forking unequally and scaly (im- 

 bricated). Trenton formation, II c, 



Orthis bellula, James. Pal. Ohio, Vol. 1, 1873, p. 103, pi. 



^^ I 8, figs. 5 a, natural size, back ; 

 5 5, magni-fied two diam. same ; 

 5 (?, magnified^ ventral; 5 6?, 



pf. &, 



P(.9 

 tm.A.G. 1855. 



3e 



5a I 



'Hi' \ 



jim ditto, hinge; 5 e, ditto, front; 

 fflim ^ '^' ditto, striae on the surface. 

 Oincmna ti group . Ill J. 



