230 



Cincinnati Society of Natural History. 



near the column, than on other parts of the body. There is no alter- 

 nation in the arrangement of the plates, nor ai^ regular circular series, 

 such as the larger circle of plates that covers the greatest convexity of 

 L. crater if or mis. It is distinguished from the latter species by this 

 want of any order in the arrangement of the plates, the absence of the 

 large circular series, and the slight convexity of the plates. It has a 

 column which is pentagonal near the head. 



It is found in the upper part of the Hudson River Group, in Warren 

 a nd Clinton counties. The specimens illustrated were presented to the 

 author by Dr. Dyke, of Lebanon, O., who found them in that vicinity, 

 and I collected it several years ago near Clarksville, associated with 

 Glyptocrinus oneali and Megalograptus welchi. It is found in the 

 rocks a little below the range of L. tuberculatus, but considerably 

 above an} T known specimens of L. crater if or mis. 



Cyclonema cincinatense, n. sp. 



[Plate IX., fig. 8, natural size ; fig. 8a, natural size, showing aperture with a little of tl'e 

 outer lip broken away ; fig. 8&, natural size of a specimen, with much of the outer lip 

 broken off; fig. 8c, magnified view of a part of the surface of the upper part of the last 

 whorl.] 



Shell rather below the medium size in this genus, and usually wider 

 than high. It consists of four or five rounded volutions, which in- 

 crease rather rapidly in size, and become more depressed upon the up- 

 per side as they approach the last whorl, which is also flattened upon 

 the lower side, from the outer lip to the columella, and forms a slight 

 concavity, as it passes the straightened lip of the latter; suture usually 

 well defined; aperture higher than wide, somewhat ovate in outline, and 

 straightened upon the inner side; inner lip slightly thickened at the 

 columella. 



Surface ornamented by revolving lines or ridges, which are beauti- 

 fully crenated or delicately cancellated by the crossing of more numer- 

 ous and finer oblique lines of more uniform size. About six or seven 

 revolving ridges, or strong lines, occur on the upper and outer part of 

 the last volution, those on the upper part being most distant from 

 each other, and between each of which there is a single fine revolving 

 line ; on the volution preceding the last, only four or five of the stronger 

 revolving lines occur, with a corresponding decrease in the number of 

 the finer ones; while on the first and second volutions the revolving- 

 lines are more uniform in size and less numerous. The revolving lines 

 on the under side of the last volution become gradually finer toward 

 the columella, until they correspond in size with the crossing oblique 

 lines, and furnish an evenly cancellated ornamentation. 



