FOSSILS OF THE DEVONIAN 249 



foiir-fiftLs as liigh as long; valves depressed-convex, perhaps partly due to 

 compression; beaks large, broad, and prominent, situated about one-third 

 of the length from the anterior end; posterior cardinal margin rapidly slop- 

 ing to below the middle of the valve, from which point the posterior end 

 rounds forward to the straight basal line; anterior end rounded, its greatest 

 length being much below the middle of the valve, above which tlie margin 

 is concave to just below the beak. Teeth and hinge unknown. On remov- 

 ing the sliell from a portion of the valve, a slight impression was seen on the 

 cast anterior to the beak, resembling that left by the removal of a muscular 

 clavicle, or ridge, but not quite satisfactory in its character. 



Surface of the shell marked only by moderately strong, irregular, con- 

 centric undulations. 



The general form of the shell is much like that of N. triqiietra Con. 

 from the Hamilton group of New York, but with a straighter basal line, much 

 larger and tumid beaks, and of very much greater size than is known in that 

 species. 



Formation and localiiy. — In the lower black slates of the White Pine 

 District, near Eberhardt Mill. Collected by Arnold Hague, esq. 



aenus LUNULICARDIUM Munster. 



LUNULICAKDUJM PEAGOSUM. 



■-IIP 

 Plate }^, figs. 9-11. 



Posidonomyaf fragosa, Meek. (Part I, page 92 aud Plate.) 



The specimens figured and described by Mr. Meek, under the name 

 Posidonomyaf fragosa, prove, on carefully uncovering the cardinal portions 

 of the specimens, to belong to the genus LunuUcardium, a genus, so far as 

 we are aware, that has only been recognized in rocks of Devonian age, 

 unless the genus Clicenocardia M. & W. should prove to be identical, about 

 which we have some doubt. In the rocks of this age in New York, it has 

 been recognized in several species, ranging from the Marcellus shales to the 

 Chemung group inclusive, one or more species being known in each forma- 

 tion. The shells are readily recognized by the broadly gaping anterior (?) 

 end, bordered by a more or less reflected margin or flange-like projecting 

 border, extending from the beak to the basal margin, which we presume is 

 analogous to the byssal opening in other forms of shell. The species 



