88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



Genus ELVINIA Walcott 



Elvinia Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. 2, p. 56. 



Description. — A large number of closely related species belonging 

 to this genus is present in the National Museum collections. Some 

 are definitely in the Upper Cambrian while others are Ozarkian. 

 The specific assignment of the various body parts seems fairly correct. 



The principal character that distinguishes the genus is the first 

 pair of glabellar furrows, which is strongly impressed, the lateral 

 parts sloping backward and united by a straight horizontal , furrow. 

 Another very short and faint pair can sometimes be distinguished 

 farther forward. An occipital furrow is present but often so shallow 

 as to be distinguished with difficulty. Dorsal furrow strong and 

 definite. 



Fixed cheeks fairly wide. Ocular lines present, usually in the 

 form of an escarpment-like edge of the more elevated portion of 

 the fixed cheek lying back of this line. Eyes of moderate size and 

 situated opposite the forward half of the glabella. 



The facial suture diverges sHghtly in front of the eyes and is 

 intramarginal for about half way. Back of the eyes it passes rapidly 

 outward in a gentle curve, thus giving a wide base to the cranidium. 

 Free cheeks wide, with a well-defined rim. Genal spines usually long. 



The pygidium of Elvinia is characterized by its clearly defined 

 rings on the axis and the broad, but more shallow, pleural furrows. 

 The axis is convex, cylindrical to sub-cylindrical in form, and it 

 usually extends nearly to the posterior margin. The pygidia of many 

 species have a wire-like raised edge which widens and thickens toward 

 the anterior angles and joins the larger segment, usually the first. 



Genotype. — Dikelocephalus roemeri Shumard. 



Range.^— Upper Cambrian — Ozarkian : New York and Pennsyl- 

 vania, and numerous localities west of the Mississippi River. 



ELVINIA ROEMERI (Shumard) 



Plate 17, figs. 9-13 



Dikelocephalus roemeri Shumard, 1861, Amer. Journ. Sci., 2nd ser., Vol. 32, 



p. 220. (Original description.) 

 Ptychoparia roemeri Walcott, 1914, Smithsonian Misc. Coll., Vol. 57, No. 13, 



p. 352. (Generic reference.) 

 Elvinia roemeri Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. 2, p. 56, 



pi. II, fig. 3. 



Observations. — The cephalon here illustrated has been chosen as 

 most nearly representing Shumard's description of the species. It 



