Orth. 



510 



c. 



foramen; 1 e, inside of ventral valve, showing area, foramen, 

 teeth, deep muscular scar. // c up to V a. 



Orthis billingsi, Hartt. Dawson's Acad. Geol. 1868, p. 

 a23 ^44, fig. 223 ; foramen triangular and of moderate 

 size ; surface ornamented by about thirty prominent 

 rounded rays, widening towards the edge, crossed 

 -P^ by some distinct concentric squamose growth-lines 



and many jSne concentric strige (not shown in the figure). 

 Rather common in the Trilobite shales, St. John, N. B.— Cam- 

 brian^ C. 



Orthis billingsi, Hartt. (1868, Dawson's Acad. Geol. 2d 



Ed. p. 644, fig. 223.) Wal- 

 cott, Bulletin No. 10, U. S. 

 G. 8. p. 17, pi. 1, fig. 1, cast 

 of ventral valve, enlarged 

 twice ; fig. 1 a^ small ven 

 tral valve (doubtfully re- 

 ferred to this species) en- 

 larged thrice ; fig. 1 J, cast 

 of ventral valve, enlarged 

 twice ; 1 c, outside of dor- 

 sal ? valve, ribs crossed by 



fine concentric wavy lines, enlarged ?5AW<?e.— Cambrian (St. 



John) formation. New Brunswick. C. 



Orthis biloba, Linn. Figure from Oollett's Indiana Report 

 Y6- X of 1881, p. 286, pi. 27, fig. 16, ventral valve, enlarged 

 twice. — Niagara limestone^ Vb. — See, also, an out- 

 line of the European species given by Ringueberg 

 llHSr"''^^2j for comparison with his new (1888) species, 0, 

 acutiloba, under that name above. 



Orthis bisulcata. See Camarella bisulcata. II c. 

 Orthis callactis ? ( Orthis ilabellulum, Sil. Res. xxi, fig. 8.) 

 105. Emmons, p. 394, fig, 105, 2. Hall, p. 105, fig. 



1^-B^'^.,^F^ 36,5. 77 (?, Trenton formation. (For figure of 

 Hall see Orthis flabellulum.) 



EJ05 2 

 Orthis borealis, Billings. Can. Nat. and Geol. Vol. 4, 1859. 



