SOME NEW DEVON IC FOSSILS 245 



more prominent by the greater elevation of the beak and conse- 

 quent greater width of the area. 



To a certain degree this structure is comparable to that observed 

 in the subgenus Beachia H. and C. (type, R. suessana Hall, 

 Oriskany, Cumberland, Md.). In this shell "the cardinal margin 

 beneath the beak [of the ventral valve] is flattened into a well 

 defined pseudoarea " [Pal. N. Y. v. 8, pt 2, p. 259]. Here however 

 is a high development of a cardinal area to a degree far beyond 

 that expressed in Beachia. Furthermore in Beachia " the short 

 inflection of the margin beginning here [on the hinge line] is con- 

 tinued along the lateral portion of the shell where it meets a similar 

 marginal inflection from the opposite valve. These produce the 

 sharp introversion of the lateral margins which is also one of the 

 characteristics of the genus Megalanteris." No such reentrant 

 margins occur in the shells under consideration. I would not 

 refer the species to the subgenus Beachia lest thereby its real 

 affinities be obscured. 



The kindness of Prof. E. Kayser of Marburg has enabled me 

 to compare my material with typical examples of the Rensselaerias, 

 R. strigiceps F. Roemer and R. crassicosta (Koch) 

 Kayser, of the lowest arenaceous Devonic of the Rhine, and my 

 lamented friend, the late Dr L. Beushausen of the Landesanstalt, 

 Berlin compared some specimens from the Presque Isle stream 

 fauna with examples of the species mentioned, in the collections 

 of that institution. 



The evidence at hand is very clear that while the specimens 

 currently referred to R. strigiceps are quite variable in 

 degree of surface striation, yet this species also bears a cardinal 

 area upon the valves. This feature is particularly well shown 

 by a valve from the Taunus quartzite of Katzenloch near Idar in 

 the Rhine province. In the main the specimens of this species 

 are somewhat more finely striated than those from the Presque 

 Isle but this is a difference notable only in the older shells 

 where by obsolescence of the lateral striae the riblets become 

 apparently less. 



x\n internal cast ofR. strigiceps, somewhat distorted, from 

 the Siegen greywacke at the iron mine Alte Mahlscheid near Her- 

 dorf illustrates the immature character of certain of the generic 

 structures. Thus the hinge plate and cardinal process are thin 

 and not perforated, the dental plates and pedicle pit rather incon- 

 spicuous and the muscular impression not sufficiently strong to 

 eradicate the marks of the shell plications. Such an expression of 



