458 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



Ptychoparia llanoensis Walcott (?) 



PL LXIV, fig. 4. 



Ptychoparia llanoensis Walcott, 1890: Proc. U. S. Nat. Mus., Vol. XIII, p. 272, PI. 

 XXI, figs. 3-5. 



The fragments that have been compared and provisionally identified 

 with this species show only the central portions of the head. The frontal 

 rim and border, separated by a narrow, raised, crenulated line on the cast 

 of the under surface of the test, and the glabella, appear to be identical with 

 those of some of the specimens of P. llanoensis. 



Formation and locality: Middle Cambrian, Livingston section, at head 

 of Davis Creek, Snowy Range, Montana. 



Ptychoparia sp. undet. 

 PL LXIY, fig. 5. 



This is a rather strongly marked form, of which only the central por- 

 tion of the head is preserved. It differs from other described species in 

 having the frontal rim project inwardly almost to the front margin of the 

 glabella. A figure is presented of the only specimen in the collection. 

 The head may be compared with the head of Ptychoparia teucer, from the 

 red sand rock of Highgate Springs, Vermont. 1 It is possible that this is a 

 strongly marked variety of P. antiquata. 



Formation and locality: Middle Cambrian, Flathead formation, near 

 Crowfoot section, Gallatin Range, Yellowstone National Park. 



Ptychoparia (?) sp. undet. 

 PL LXIY, fig. 3. 



This is a clearly marked form, represented by the central portion of 

 the head. The small eye lobes and strong postero-lateral limbs suggest 

 Ptychoparia eryon Hall, 2 but the glabella is less elongate and the frontal limb 

 is marked by a rounded rim. 



Formation and locality: Middle Cambrian, Crowfoot section, Gallatin 

 Range, Yellowstone National Park. 



1 Tenth Ann. Kept. U. S. Geo]. Surv., 1891, PL XCVI, fig. 3. 



2 Sixteenth Ann. Rept. New York State Cab. Nat. Hist., 1863, PI. VIII, figs. 16, 31. 



