262 



PAL^ONTOLOGfY OF NEW-YORK. 



proves the identity of the t'.vo, while the S. odopHcatus can only be considered as a represen- 

 tative form in the Carboniferous period. 



This species is one of the most common forms in the Niagara group, always associated with 

 the following species, which is far less abundant. 



Fig. 2 a. A small specimen, having the cardinal extremities scarcely extended. 

 Fig. 2 b, c. Views of specimens where the cardinal line is extended into mucronate points. 

 Fig. 2 d. An unusually large specimen, having the hinge-line less extended than the preceding. 

 Fig. 2 e. A specimen where the length and breadth are nearly equal, though the specimen ap- 

 pears to retain its natural proportions. 

 Fig. 2 /. Front view of fig. 2 b. 

 Fig. 2 g. Front view of 2 e. 

 Fig. 2 h, i. Profile views of different specimens. 

 Fig. 2 k. An enlargement of the surface, showing the longitudinal strise crossing the lamellae. 



Position and locality. In the shale of the Niagara group at Lewiston, Lockport, Rochester, 

 Wolcott, and other places. 



623. 6. SPIRIFER CRISPUS. 



PL, LIV. Fig. 3o-fe. 



Terebratula crispa. Hisinger, Act. R. Acad. So. Holmiensis, 1826, tab. vii, fig. 4. 



— — Id. Anteckn. iv, t. vii, fig. 4. 



Delthyris crispus. Dai.man, Vet. Acad. Haiidl. 1827, pag. 122, tab. iii, fig. 6. 



— — Hisinger, Petref. Suecica, 1839, p. 73, t. xxi, f. 5 a, b. 

 Spirifer crispus. Sow. in Murchison's Sil. System, 1839, pag. 624, pi. 12, fig. 8. 

 Delthyris staminea. Hall, Geol. Rep. 4th Dist. N. York, 1843, pag. 105, fig. 3, and p. 106. 



Shell subrhomboidal (ventral valve semicircular), gibbous; valves very unequal, the dorsal 

 one extremely convex, and the beak extended and incurved ; surface marked by five or six, 

 rarely eight, plications on each valve, which are sometimes obsolete, concentrically marked by 

 fine elevated thread-like strige ; area broad, with the cardinal extremities short ; foramen long, 

 narrow. 



This shell is readily distinguished from the last, by the slightly elevated and often obsolete 

 plications, which are crossed by fine, closely arranged simple strice. A careful examination of 

 these striae under a magnifier shows that, between and upon the striae, the surface is thickly set 

 with minute setose points, giving a semistriated appearance to the surface. This feature is not 

 ordinarily visible, and it appears to have been abraded by very slight attrition. In the more 

 perfect condition of the shell, the beaks of the two valves are widely separated, presenting a 

 broad cardinal area ; but in many specimens, either from pressure or other causes, the beaks 

 approach each other, and the proportions of the shell differ little from the preceding species. 



A comparison with Swedish specimens shows no difference of character ; and it is there, as 

 here, associated with S. sulcatus in the same rock, and in the same locality. The same is 

 likewise true of these species in the Wenlock formation of England. This one, like the pre- 



