NO. 13 DIKELOCEPHALUS AND OTHER GENERA 409 



Calvinella spiniger (Hall) — Continued. page 



Fig. 17. (X 1.25.) Thoracic segment. (i35d.) U. S. National 

 Museum, Catalogue No. 58654. 

 18 and 19. (X 1.25.) Pygidia associated with the cranidia repre- 

 sented by figs. II, 13, and 15. (83-.) U. S. National 

 Museum, Catalogue Nos, 58655 and 58656. 

 The specimens represented by figs. 11-19 are from localities 83' 

 and 1353, Upper Cambrian : St Lawrence formation ; " fifth trilobite 

 bed " of Owen, Trempealeau, Wisconsin. 

 20. (X 2.) Small cranidium in fine sandstone with strong frontal 



rim. U. S. National Museum, Catalogue No. 58657. 

 21 and 2ia. (Natural size.) Cranidium preserving its natural 



convexity. U. S. National Museum, Catalogue No. 58658. 

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

 logue No. 58659. 

 23 and 23a. (Natural size.) Dorsal and side views of a pygidium 

 preserving its natural convexity. U. S. National Museum, 

 Catalogue No. 58660. 

 The specimens represented by figs. 20-230 are from a fine-grained 

 sandstone of locality 83^ Upper Cambrian ; An upper horizon of 

 the St. Lawrence formation near Trempealeau, Trempealeau County, 

 Wisconsin. 



