20 PROCEEDINGS OF THE NATIONAL MUSEUM vol.68 



PRIONIODELLA INFORMATA, new species 



Plate 10, figs. 19, 20 



Tooth slightly bowed with basal outline almost straight, slender 

 spinelike denticles on upper side increasing in length from either 

 side to the middle. Denticles separated by a little more than their 

 own width and occasionally a small denticle between each pair of 

 larger ones. One end of bar somewhat rounded. 



Occurrence. — Mississippian (Hardin sandstone) : Mount Pleasant, 

 Tenn. 



Gotypes.— Cat No. 10991, U.S.N.M. 



PRIONIODELLA BREVISPINA, new species 



Plate 10, fig. 21 



Characterized by the thick bar, relatively short length with one 

 end (presumably anterior) much wider and blunter than the other, 

 and subequal size of denticles with every third and fourth one 

 slightly larger. In all, fifteen denticles with one or two at either end 

 shorter and much smaller than all the others. 



Occurrence. — Mississippian (Hardin sandstone) : Mount Pleasant, 

 Tenn. 



Holotype.—Cat. No. 10993, U.S.N.M. 



PRIONIODELLA GRACILIS, new species 



Plate 10, figs. 22, 23 



Bar rather slender, of moderate length with a short spinelike 

 downward projection at its Avider end. Upper side crowned with 

 about 9 long, slender, separated denticles with a moderate back- 

 ward inclination. 



Occurrence. — Mississippian (Hardin sandstone) : Mount Pleasant, 

 Tenn. 



Goty pes.— Cat. No. 10992, U.S.N.M. 



PRIONIODELLA ROBUSTA, new species 



Plate 10, fig. 24 



Distinguished from P. gracilis by its stronger and quite erect 

 denticles. The species also shows no sign of the anterior spurlike 

 downward projection. 



Occurrence. — Mississippian (Hardin sandstone) : Mount Pleasant, 

 Tenn. 



HoJotype.— Cat. No. 10990, U.S.N.M. 



