214 University of Texas Bulletin 



Fig. ^lA^a, .Medlicottia WMtneyi nov. sp. — ^Zone of Perrinites (Leonard forma- 

 tion). — Two miles west-northwest from Iron Mountain, Glass 

 Mountains. 



Fig. 41, external suture of specimen illustrated in fig. 42-^5, 45a; 

 natural size. 



Fig. 42, venter; fig. 43, front; fig. 44, side view; natural size. 



Fig. 45, front of inner wborl of the same specimen, showing the 

 two rows of tubercles replacing the sharp keels ; natural size. 



Fig. 45a, the same; twice natural size. 

 Fig. 46-52. .MedUcottia Burckhardti nov. sp. — Zone of Waagenoceras (Word 

 formation). — Junction of Gilliam and Road canyons, Glass 

 Mountains. 



Fig. 46, side view; fig. 47, venter; fig. 48, cross-section of small 

 specimen; natural size. 



Fig. 49, internal suture of the preceding specimen, but belonging 

 to the next larger whorl; natural size. 



Fig. 50, the same ; twice natural size. 



Fig. 51, side view of mature specimen illustrated in Plate II, fig. 

 1-2; natural size. 



Fig. 52, cross-section of the same specimen ; natural size. 



