312 Review of the New York Geological Reports. 



Plate 35, p. 104, Hall's Report. 



'tU-^As" 



PI. 35, fig. 1. Strophomena suhplana. 



2. ;S'. depressa, (lower valve.) 



3. S. striata. 



4. /S*. transversalis. 



The deflected portion of fig. 2 is usually not so long, nor the 

 undulations so numerous as in Murchison's figure of the same 

 name, nevertheless Hall thinks the English and American fossil 

 the same species, since this shell of different ages, from the same 

 rock, has variations of the same kind. There is a wrinkled Stro- 

 phomena found in the West which bears considerable analogy 

 to this same S. depressa. The hinge-line of the New York spe- 

 cies is however more prolonged, and terminates in sharper an- 

 gles ; the deflected portion probably of less area, and the undu- 

 lations of the flat surface fewer. The western fossil here re- 

 ferred to, occurs in the upper part of the blue limestone and mar- 

 lite, (rather lower than the beds supposed to be equivalent to the 

 Niagara group,) but Hall says the New York species commences 

 in the Clinton group, yet it is most abundant in the Niagara 

 group. The western fossil is known as the /S*. undulata.* Both 

 figs. 1 and 3, resemble species found in the blue limestone of 

 the West, but we are not prepared to decide upon identity 

 without comparing the fossils themselves. The New York speci- 

 mens of fig. 4, differ from Murchison's figure of the same name 

 only in being a little " smaller and less prominently ribbed." 



* The fossil referred to by Dr. Owen is doubtless the Strophomena (Leptana) 

 ttenui- striata, a species from the Llandeilo flags of Wales, and common in the 

 Trenton limestone of New York. — Eds. 



