DESCRIPTIONS OF SPECIES 367 



face appears to be covered with fine radiating strise, which are inter- 

 rupted by the concentric striae, thus giving the surface a fimbriate 

 appearance. 



On the interior of the pedicle valve are two short dental plates, diverg- 

 ing slightly more than the sides of the sinus. 



The cardinal area of this species is high, occupying in some specimens 

 as much as a third of the total height of the valve. The strength of 

 the ribs on the brachial valve varies somewhat in different specimens, 

 but they are always much less marked than those of the pedicle valve, 

 and they are usually quite obsolete. 



The species to which this most nearly approaches is the variety of 

 S. crispus Hisinger found in the Coralline limestone at Schoharie. In 

 this variety the ribs are much fainter than in the normal S. crispus of the 

 Niagara shales and limestones of western New York. In many speci- 

 mens from Schoharie the ribs are almost obsolete, comparing well with 

 their character in S. eriensis. The sinus of the Schoharie specimens is 

 subangular, and the fold flattened much as in the Bullhead limestone 

 species. This variety is also proportionally higher than the normal 

 form, giving a subrhomboidal outline to the pedicle valve, which strongly 

 recalls S. eriensis. In general the ribs of this latter species are slightly 

 broader and rather more flattened on top than is the case in the Coral- 

 line limestone species, and the interspaces are somewhat narrower. 

 Taking all the variations into consideration, a very close relation must 

 be accepted as existing between the two species. 



The specimens described by Whitfield as S. vanuxemi from the hydraulic 

 limestone (Manlius ?) of Peach point, Put-in-bay, Lake Erie, resembles 

 rather more closely the normal S. crispus than it does the typical S. 

 vanuxemi of the Manlius limestone of central New York. This similarity 

 to the Niagaran species was observed by Whitfield. The strong plica- 

 tions and greater width separate it from S. eriensis. 



Most of the specimens of S. eriensis were found at Williamsville. A 

 few, however, came from the cement quarries in North Buffalo. 



Width of the pedicle valve illustrated, 10 millimeters; length, 8.5 

 millimeters. Width of the brachial valve illustrated, 7.5 millimeters; 

 length, 6 millimeters. 



WHITF1ELDELLA SULCATA (VANUXEM) 

 (Plate 22, figures 2a-d.) 



1842. Atrypa sulcata Vanuxem. Geological Report of the Third District of New 



York, page 112, figure 5. 



1843. Atrypa sulcata Hall. Geological Report of the Fourth District of New York, 



page 142, figure 5. 

 1859. Merista bisulcata Hall. Paleontology of New York, volume 3, page 253. 



