The Lift'-Uistury of >Sj>irif('i' hf'rif<. 151 



known in America, identified by Ilall as the true Spirifer 

 cri^pn^, Hisinger. It occurs in the Niagara shales in the west- 

 ern part of New York State ; most abnndantly about Lockport 

 and Lewistown. 



1. It is of sub-rhomboidal form, rounded at the sides; the ven- 

 tral valve is semi-circular. This peculiar shape includes a short 

 hinge-line, either as short or shorter than the greatest width of 

 the shell. 



3. The valves are unequal in convexity, "very unequal," the 

 ventral one extremely convex, the dorsal not so much so, (This 

 character is also seen in well-preserved specimens of S. Icevis.) 



3. Beaks moderately extended and incurved over the hinge- 

 area : they may be much separated, or approach each other 

 closely, making — 



4. A hinge-area, either broad and prominent or low and 

 narrow ; this latter being the case when the hinge is extended, 

 and then the form approaches that of S. sulcatus. The normal 

 or typical form of crispus may be considered as possessed of a 

 high cardinal area, the extremities of which are short. 



5. The aperture is triangular and rather narrow, and is not 

 covered with a pseudo-deltidium, in specimens joreserved. This 

 is most likely due to the fact, that the pseudo-deltidium was 

 not completely calcified in the living animal, and during fossili- 

 zation was lost. 



The radiating plications are few, — from four to eight, — but 

 only slightly elevated and rounded, and often obsolete, and the 

 inside casts are smooth. As to this variation, note crispus of 

 the Coralline limestone, and the var. simplex of Indiana and 

 the West, also the smooth type, hicostatus. 



The radiating folds are marked by fine concentric lines ; 

 these, by aid of a magnifying glass, are seen to answer to 

 Hall's description — ''and upon the strise, the surface is thickly 

 set with minute setose points, giving a semi-striated appearance 

 to the surface. This feature is not ordinarily visible, and it 

 appears to have been abraded by very slight attrition." Hall's 

 Pal. of N. Y., Vol. 2, p. 262. Hall finds no reason to separate 

 this from the Swedish species, nor from that of the Wenlock of 

 England. 



S. bicostutus, Conrad, dijffers from crisp)us in the more dis- 



