172 PROCEEDINGS OP THE ACADEMY OF 



the non-plicated varieties of the N.York Upper Silurian P. sinrale, 

 than it is to any of the other Carboniferous species known to me, 

 thongli its first two volutions are more compactly coiled together 

 than those of that species. 



Locality and position. Greentown, Summit Co., Ohio. Coal- 

 measures. 



HOLOPEA (CYCLORA) NANA, Meek. 



Shell very small, subglobose, wider than high ; spire much de- 

 pressed ; volutions three, rounded, increasing rapidly in size, so 

 that the last one forms the larger part of the shell ; suture deep 

 or almost channelled ; surface smooth ; umbilicus small ; aperture 

 subcircular; lip simple. 



Height of the largest specimen seen, 0.05 inch ; breadth, 0.01 

 inch. 



This little shell seems to be quite abundant, and from the fact 

 that the larger specimens present considerable uniformity of size 

 and general appearance, I can scarcely doubt that they are adults. 

 It will probably fall into the genus Cyclora, Hall (Am. Jour. Sci. 

 and Arts, vol. xlviii. p. 294, 1845), and would seem to agree closely 

 in size and form, as near as can be determined from a description 

 alone, with the typical species C. minuta. So far as I have been 

 able to determine, its inner lip, however, does not appear to be 

 reflected over the minute umbilicus, as is said to be the case in 

 that shell. The G. minuta came from the Cincinnati group at 

 Cincinnati, and it is very improbable that it ranges up to the 

 horizon at which the specimens under consideration were ob- 

 tained. 



Locality and jiosition. Clinton, Ohio. Silurian. 



ORTHOCERAS ? ISOGRAMMA, Meek. 



The only specimens of this shell that I have seen are flattened 

 by accidental pressure. The most nearly perfect specimen in the 

 collection is 2.80 inches in length, with a breadth (as seen flattened 

 in the matrix), at the larger broken end, of about 0.95 inch, and 

 with sides diverging from the smaller, rather bluntly pointed ex- 

 tremity, at an angle of about 18°. At and near the smaller end 

 the surface is marked by very minute, crowded, transverse, or 

 annular striae. About three-fourths of an inch farther up, these 



[August 15, 



