513 



Orthis. 



Orthis demissa ? Oast showing muscular scar, 854-41, 

 (00, p. 236) in Sherwood's coll. Charlestown, Tioga Co. Fa. 

 from Upper Chemung^ VIII g, 



Orthis dichotoma. (Hall, Pal. N. Y. Vol. 1, 1847.) Em- 

 mons, Amer. Geol. Vol. 1, pi. 2, p. 195. fig. 

 13; valves unequally convex; folds fork 

 half way from beak to base; crenulations 

 indistinct. — III h. Blue limestone of Ohio 

 PI 9 (Hudson river) formation Note. — S. A. 

 Miller makes this and Orthis fissicosta (Hall) the same. 



Orthis disparilis. (Conrad, Proc. A. N. S. Phil. 1843.) 



^ Em. A. G. I, ii, 1855, 

 % 194, pi. 9, fig. 4 «, 5, <?, 

 fY a small shell ; hole nar- 

 CanV row; about 28 folds, 

 half of them beginning under the beak (umbo) crossed by 

 many concentric lines. Black river and Trenton, — Geol. Can. 

 1863, p. 130, fig. 60 a^ ventral valve; &, side view. CKazy 

 limestone^ II h^ g. 



lie. Em.AG.ia^iJ. 



Orthis dubia. 



( Hall, Trans. Alb. Inst. 1856, Vol. 4. Whit- 



g field. Bull. 3, 



Am.Mus.N. H. 

 N. Y. 1882, pi. 

 6, figs. 1 to 5.) 

 ^) Collett^s Indi- 

 ana Rt. 1882, p. 



324, pi. 29, fig. 1, back view of fat specimen from Bloomington, 

 Ind. ; figs. 2, 3, 4, a larger specimen from Spergen Hill ; fig. 5, 

 inside of ventral valve of large specimen from Paynter's Hill. 

 Subcarboniferous. XI Note. — Extremely like Orthis miche- 

 lina^hvii grows only one-tenth as large ; perhaps its young? 

 Collett. 



Ind:' IS^X. n, 29. 



/J. 



Orthis electra. Billings, Pal. Foss. Vol. 1, 1862. Geol. 

 Can. 1863, p. 231, fig. 246 «, ventral valve ; 5, side 

 view. Quehec group {Lower Silurian). II, 



246 

 a 6 



&.C 



