44 Cincinnati Society of Nafnral Hi-story 



distinct. The second is much shorter, and comparatively 

 indistinct; its posterior margin is on a line with the inner 

 termination of the median rib of the middle pair of lobes. The 

 reflexed margin or doublure extends back for almost half the 

 length of the pygidium along its middle part. The entire 

 exterior surface of the pygidium is covered by small granules, 

 about a sixth of a millimeter in diameter. 



Found in the Whitewater division of the Richmond 

 group, at Richmond, Indiana, by John Misener. The species 

 evidently is closely related to Amphilichas halli, Foerste, from 

 the Corryville member of the Maysville group, at Cincinnati, 

 Ohio. 



The Misener collection contains also a fragment of a 

 pygidium of Arctmurus harrisi. Miller, obtained from the 

 immediate vicinity of Richmond, Indiana. In Bassler's Bib- 

 liographic Index of American Ordovician and Silurian Fossils, 

 the type is listed as coming from the Liberty member of the 

 Richmond, near Waynesville, Ohio. Figure 1 on plate III 

 is a diagrammatic representation of the pygidium of this species. 

 It is characterized chiefly by the acute termination of the axial 

 lobe. The three pairs of lateral lobes are rounded and sub- 

 equal. 



Tripteroceras (Lambeoceras) richmondensis, sp. nov. 

 Plate I, Figs. 3 A, B, C, D; Plate III, Fig. 2 



Orthoceracone greatly compressed, transverse section 

 (figure 2, on plate III) lenticular, the lateral edges acute. 

 Radius of curvature across the middle of the septa slightly 

 more than half of the chord connecting the ends of the arc 

 formed by the septa; for instance, the radius of curvature of 

 the lowest septum preserved in the specimen figured is 28 

 millimeters, and the lateral diameter of the shell at this point 

 is 53 millimeters. Along the ventral side of the shell the 

 transverse curvature of the septa is somewhat greater than 

 on the dorsal side, causing the suture line on this side to rise 

 more rapidly than on the dorsal side until within a distance 

 of 5 to 7 millimeters of the acute lateral angles of the shell. 



