Ehyn. 



882 



edge; 1 a, vertical section, ^ distance from front; fig. 4, tooth?; 

 plate 29, fig. 1, upper, 2, lower mandibular teeth ; 1 a^ outline of 

 forward angle, worn by use : 1 5, <?, other forms of same 3 2 a^ 

 outline forward angle of another tooth somewhat worn; 

 smaller, narrower, smoother, less thick and massive than R, 

 frangens. and easily distinguished by the cutting edge; 1 and 2 

 taken from a group of four found together (belonging to a 

 single fish) at Sandusky and Delaware, Ohio, in the Cornifer- 

 ous limestone. VIII a, 



Rhynchonella abrupta, Hall, 10th Report, N. Y. State 

 Mus. p. U ; Pal. N. Y. Vol. 3, 1859, 1861, page 228, plate 31, 

 fig. 3, ^, 5, dorsal and ventral valves of a well marked speci- 

 men ; c, d^ front and hinge view of another. {See Appendix.) 

 Perhaps an extreme variety of R. nucleolaia (Hall.) Jn N. 

 Y. in shaly limestone of VL In Pennsylvania, Perry Co., 3 

 m. E. of Ikesburg, Spec. 12713 (wrongly marked Eatonia me- 

 dialis^ Van. in 000, page 166. It is closely allied to R, velli- 

 Gota, G. B. S.) Lower Helderlerg. VI, 



Rhynchonella acadiensis, Davidson. Dawson's Acadian 



xiii .^i:^ ^Jii^ 9^ Geology, 1868, p. 295, fig. 94, na- 



turalsize.,^ndmagni/led ; founded 

 on two specimens only from the 

 Carhoniferous shell limestone of 



Daw. '^"'•^^ Brookfield, Nova Scotia; quite 



distinct from the young of R. pugnusj and R, pleurodon. 



(Davidson, in Dawson.) — XIII ? 



Rhynchonella acinus, Hall. From Oollett's Indiana, 1881, 



page 306, plate 26, fig. 7, enlarged 4 times, back valve of reg- 

 ularly ovate specimen; fig. 8—11, enlarged, back, front, belly, 

 and side view of a somewhat larger specimen, of the common 

 kind. Niagara^ Vh. 



R. aoutiplicata^ Hall. R. acutirostris^ Hall. R. aequival- 

 vis. Hall. R. oequiradiata, Hall. R. ainslmi, Winchell. 



