PALEOZOIC TIME — CAMBRIAN. 



477 



562. 



New York. Sandstones and calcareous beds represent the Upper Cambrian in 

 Arizona and Texas, and 

 limestones and shales in 

 Nevada, Idaho, and Mon- 

 tana, and probably in 

 British Columbia. 



The chief character- 



563. 



istic of the Fauna, dis- 

 tinguishing it from that 

 of the preceding epoch, 

 is the almost total inde- 

 pendence in species, so 

 far as now known; the 

 absence of Paradoxides, 

 and the substitution of 

 Trilobites of the genus 

 Dicellocephalus, of 

 which 30 species have 

 been described ; and, 

 further, the multiplica- 

 tion of Gastropods of 

 coiled forms. 



1. Rhizopods, Sponges, Graptolites, Cystoids. — The green sand of the beds of 

 Wisconsin is probable evidence of the abundant presence 

 of Ehizopods, since similar grains from later rocks were 

 shown by Ehrenberg to have the form of casts of the in- 

 terior of Rhizopod shells. Remains of Sponges and of 

 Cystoids, allied to those of the earlier Cambrian, occur in the 

 beds. One of the Graptolites is represented in Fig. 564, 

 and a branch of the same enlarged in Fig. 565. 



2. "Worms. — The Scolithus (S. Uneai^is) from the Potsdam 

 sandstone is represented in Fig. 566. The fossil is the filling of the vertical 

 burrow made by the worm in the sand. 



666. 



Cbustacbans. — Fig. 562, Leperditia Argeuta Walc; 

 563, Anomalocaris Canadensis (1) Whiteaves. 



564. 



565. 



Dendrograptus Hal- 

 lianus. Prout. 



Kg. 566, Scolithus linearis. Hall. 



567, Cruziana eimilis, supposed track of a worm. Billings. 



