424 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DESCRIPTION OF PLATE 51 



PAGE 



Dolichometopus tontoensis Walcott 373 



Fig. I. (Natural size.) A nearly complete dorsal shield, showing en- 

 larged fifth segment. U. S. National Museum, Catalogue 

 No. 62685. 

 la. (Natural size.) A broken dorsal shield, with median nodes on 

 thoracic segments. U. S. National jNIuseum, Catalogue No. 

 62686. 



The specimens represented by figs, i and la are from locality 746, 

 Middle Cambrian : Bright Angel shales ; Grand Canyon, Arizona. 



lb. (Natural size.) Hypostoma and side profile. U. S. National 

 Museum, Catalogue No. 62687. 



ic. (Natural size.) Small convex cranidium. U. S. National 

 Museum, Catalogue No. 62688. 



id. (Natural size.) Cranidium. U. S. National Museum, Catalogue 

 No. 62689. 



id'. (X2.) Free cheek. U. S. National Museum, Catalogue 

 No. 62690. 



id". (Natural size.) Free cheek. U. S. National Museum, Cata- 

 logue No. 62691. 



le. (Natural size.) Thoracic segment. Right half restored. U. S. 

 National Museum. Catalogue No. 62692. 



if. (Natural size.) Large pygidium. U. S. National Museum, Cata- 

 logue No. 62693. 



i^, ig'. (Natural size.) Dorsal and side views of a pygidium. U. S. 

 National Museum, Catalogue No. 62694. 



ih. (Natural size.) Small pygidium. L'. S. National Museum, 

 Catalogue No. 62695. 



The specimens represented by figs, ib-h occur as casts in a hard 

 gray sandstone and retain most of their natural convexity. They 

 are from locality 74, Middle Cambrian: Tapeats sandstone; Nun- 

 koweap Valley, Grand Canyon, Arizona. 



Dolichometopus baton Walcott 362 



Fig. 2. (X2.) Broken dorsal shield, partly restored. U. S. National 

 Museum, Catalogue No. 62696. 

 2a. (X3-) Imperfect dorsal shield with hypostoma showing 

 beneath the glabella. U. S. National Museum, Catalogue 

 No. 62697. 

 2b. (X2.) Cranidium with free cheeks outlined. U. S. National 

 Museum, Catalogue No. 62698. 



The specimens represented by figs. 2, 2a-b are from a fine argil- 

 laceous shale at locality 3 j, Middle Cambrian : Wolsey ? shale ; 

 6 miles (9.6 km.) west-northwest of Scapegoat IMountain, Powell 

 County, Tklontana. 



