NATURAL SCIENCES OF PHILADELPHIA. 89 



GYKOCERAS (NAUTILUS ?) INELEGANS, Meek. 



Shell attaining a large size, subdiscoidal. Volutions about two 

 and a half to three, increasing rapidly in size, having a somewhat 

 greater dorso-ventral than transverse diameter, being moderately 

 compressed on each side, narrowly rounded over the periphery, 

 and rounding regularly into the umbilicus, which is of moderate 

 depth and distinctly narrower than the dorso-ventral diameter of 

 the outer whorl. First turn apparently slightly embraced by the 

 second, which seems to become free toward the aperture. Septa 

 rather distant, deeply concave on their anterior faces, and all 

 crossing the sides and periphery with very slight backward curves ; 

 separated from each other on the periphery b}^ spaces equalling 

 about half the dorso-ventral diameter at the point of measurement. 

 Body chamber large, or forming half the outer volutions ; aperture 

 not expanded ; lip sinuous on the outer side. Surface of cast 

 showing, on the inner volutions, some traces of rather distant 

 transverse ridges, which become nearly or quite obsolete on the 

 outer turn. Siphuncle and finer surface markings unknown. 



Greatest diameter across the disc of a specimen a little com- 

 pressed by accidental pressure, nine inches ; dorso-ventral dia- 

 meter of last turn near the aperture, 4.10 inches; transverse 

 diameter of same, 3.50 inches. 



This is another form in reo;ard to the generic characters of 

 which I am in doubt. Its more rapidly expanding volutions, 

 more rounded periphery, proportionally narrow umbilicus, and 

 closely contiguous, or even slightly embraced inner turns, give it a 

 much more nautiloid look than the last, and I should scarcely 

 hesitate to refer it to the genus Nautilus, if it were not for the 

 fact that the outer volution seems to be a little detached at the 

 aperture. Still, this may possibl}- be due to compression. 



Locality and iwsition. Corniferous group, Marion County, 

 Ohio. 



CRUSTACEA. 



PROETUS PLANIMAKGINATUS, Meek. 



Pygidium depressed, semi-elliptic, the length and breadth being 

 nearly as five to seven ; anterior margin gently arcuate or convex 

 in outline; posterior somewhat narrowly rounded; lateral margins 

 diverging forward, with slightly convex outlines, to ,the anterior 

 1871.] PART L— 7 



