NO. 3 CAMBRIAN AND OZARKIAN TRILOBITES I3I 



PAGE 



Holteria problcmatica (Walcott) 93 



Fig. 17. (X4-) Dorsal view of a very small cranidium. U. S. Nat. 

 Mus., Cat No. 24606a. (See text figure 13.) 

 18. (X I.) A larger cranidium. U. S. Nat. Mus., Cat. No. 24606b. 

 19- (X I-) A large, almost complete cranidium. U. S. Nat. Mus., 

 Cat. No. 24606c. 



20. (X I.) A small pygidium. U. S. Nat. Mus., Cat. No. 246o6d. 



21. (X I-) Largest pygidium in the collections. U. S. Nat. Mus., 



Cat. No. 246066. 



Matrix, gray limestone. 



Upper Cambrian. (Loc. 58) : Eureka District, Nevada. 



Wilbernia pcro (Walcott) 124 



Figs. 22, 23. (Natural size.) Dorsal and side views of the type crani- 

 dium. U. S. Nat. Mus., Cat. No. 23859. 



Matrix, limesfone 



Upper Cambrian, Wilberns formation. (Loc. 70) : Morgans Creek, 

 Burnet County, Texas. 



Desmetia annectans (Walcott) 83 



Figs. 24, 25. (X2.) Dorsal view and side outline of the type cra- 

 nidium. U. S. Nat. Mus., Cat. No. 24571. 



Matrix, thin-bedded limestone. 



? Ozarkian, Goodwin formation. (Loc. 201) : Eureka District, 

 Nevada. 



Irvingella major Ulrich and Resser MSS 98 



Fig. 26. (Natural size.) Restoration based on the photograph of the 

 upper specimen in fig. 27. 



27. (Natural size.) Several somewhat abraded cranidia. 



28. (Natural size.) Front view of cranidium illustrated in fig. 26. 



29. (Natural size.) Side view of group of cranidia. Figs. 26-29 on 



one slab, U. S. Nat. Mus., Cat. No. 70238. 



Matrix, micaceous sandstone. 



LTpper Cambrian, Franconia (Micaceous shale member) formation. 

 (Loc. 8on) : Ableman. Wisconsin. 



