SOME NEW DEVONIC FOSSILS 269 



Stropheodonta patersoni Hall protype praecedens nov. 



See S. patersoni Hall and S. in equiradiata Hall. Palaeontology 

 of New York. 1867. 4: 87, 90 



Professor Hall noted in his description of the two species cited 

 above, both from the Schoharie grit and Onondaga limestone that 

 while in normal forms distinction is readily made, many shades of 

 transition in style of surface sculpture are found. The shells are 

 both regularly convexo-concave species with denticulate hinge 

 with the surface ornament fundamentally consisting of fine elevated 

 and fasciculate striae, each pair of larger ones including 6 to lo 

 finer, multiplication of the larger consisting in the superior devel- 

 opment of the median stria in the fascicle. These lines are finely 



Stropheodonta patersoni protype praecedens 



reticulated by concentric elevated striae. Superinduced on this 

 ornament are, as a species character in S. patersoni, con- 

 centric discontinuous corrugations affecting chiefly the intervals 

 between the primary striae. These occur faintly and sporadically 

 in S. inequiradiata. Billings figures [Palaeoz. Foss. pi. 2, 

 fig. 3] from division i of the Gaspe series, between Cape Rosier 

 and Grande Greve a specimen identified as S. v a r i s t r i a t a 

 Conrad in which such corrugated exterior is present, and we have 

 already commented on this structure. He also insists that there 

 is no distinction between this shell (and species) and S. inequi- 

 radiata except that the former is of smaller size. Compari- 

 son of typical material representing these species however demon- 

 strates that notwithstanding the common possession of the cor- 



