38 



Found by Geo. K. Greene in the Coal Measures, on Elkhorn 

 Creek, in Kentucky, and now in the collection of Wm. F. E. 

 Gurley. 



GONIATITES MONTGOMERYENSIS, n. sp. 



Plate IV, Fig. 12, lateral view; Fig. 13, ventral view; Fig. 14, 

 surface form of a septum. 



Species below medium size, globose, volutions slowly expanding. 

 There are between three and four volutions preserved, in our 

 specimen, and, apparently, an entire shell would have more than 

 six volutions; part of the dorsal margin of each is exposed in the 

 deep funnel-shaped umbilicus. The volutions are rolled in the 

 same plane, and increase much more rapidly in the transverse, 

 than in the dorso-ventral diameter. At first, the transverse 

 diameter is not more than twice as much as the dorso-ventral, 

 but, at the end of our specimen, which is somewhere in the fourth 

 volution, the transverse diameter is three and a half times the 

 dorso-ventral and doubtless the end of the volution of an entire 

 shell has a transverse diameter five or six times as great as the 

 dorso-ventral. The ventral side is broadly convex and the dorsal 

 side correspondingly concave, for the width of the inner volution, 

 and between that and the margin, tie outer volution is beveled to 

 the form of the funnel-shaped umbilicus. The lateral side of a 

 volution consists of a sharp denticulated edge. The umbilicus is 

 like a hollow cone or funnel bordered by a sharp denticulated 

 mai-gin. 



Six furrows arise, at the margin of the umbilicus, at depres- 

 sions between the denticulations, and are directed forward at an 

 angle of about forty-five degrees, across one fourth of the width 

 of the ventral side, and then cross the middle part of the ventral 

 side in a slightly undulating line. These furrows divide a volution 

 into six subecjual parts, though the distance between them is not 

 uniform and does not increase regularly with the growth of the 

 shell. They cross the shell without any reference to the septa or 

 chambers. The air chambers are not of equal length, but they do 

 not increase in proportion to the increasing size of the shell. The 

 septa cross the ventral side in transverse waving lines. A septum 

 curves from the uml)ilicus forward and back in the form of a half 

 circle and then forms a retral subangular bend aud again curves 

 forward and back in the form of a half ellipse, and again forms 

 a retral subangular bend and curves forward over the middle 

 part of the ventral side somewhat in the form of a half circle de- 

 pressed in the middle part so as to make it bifid. There are, 



