250 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1915. 



Phyllocarida 



Ostracoda 



Eurypterida 



Limulava 



Agiaspina 



Trilobita 



which for convenience is correlated with the Apodidse. From this 

 stock it is assumed that the Branchiopoda came, and from the 

 Branchiopoda stock three distinct branches were developed prior to 

 or during Cambrian time. Of these the one of greatest interest in 

 the present connection is that on the right of the diagram. In this 



line of descent it is assumed 

 that the Trilobita are di- 

 rectly descendent from the 

 Branchiopoda, and forms 

 grouped under the order 

 Agiaspina are derived from 

 the Trilobita. The order 

 Limulava is considered as 

 being intermediate between 

 Agiaspina and the Euryp- 

 terida, and that the two 

 orders Limulava and 

 Agiaspina serve to connect 

 the Trilobita and the Eu- 

 rjrpterida. 



The line of descent of 



Fig. 1.— Theoretical evolution of Cambrian Crustacea from iha varioUS 2'enera of the 

 the Branchiopoda. c i -r 



Mesonacidse or the Lower 

 Cambrian series^ is indicated on plate 14, from figures 1 to 9, as 

 stated in the description of the plate.^ 



MIDDLE CAMBRIAN CRUSTACEANS." 



Examples of a few others of the Middle Cambrian crustaceans 

 found at the great quarry are illustrated on plate 15. 



branchiopoda 



- - Apodids 



DISCOVERY OF ANOTHER CAMBRIAN FAUNA IN THE CANADIAN 



ROCKIES. 



During the summer of 1911 a Smithsonian expedition, in coopera- 

 tion with Mr. Arthur O. Wheeler, of the Alpine Club of Canada, 

 visited the Robson Peak district.* My son Charles, who accom- 

 panied the party, brought back a few Cambrian fossils picked up 

 while hunting and told me that ridge after ridge encircled the great 

 Robson Peak with rocky layers, all sloping back toward and under 

 the mountain. This suggested an opportunity to study another 



1 Walcott : Fauna of the Lower Cambrian or Olenellus zone, Tenth Ann. Rept., U. S. 

 Geol. Surv., pt. 1, 1890, pp. 509-763. 



Olenellus: A large trilobite characteristic of the Lower Cambrian roclis. See pi. 14, 

 fig. 9, this paper. 



2 Walcott : Olenellus and other genera of the Mesonacidse, Smithsonian Misc. Coll., vol. 

 53, no. 6, 1910. 



2 Smithsonian Misc. Coll., vol. 57, no. 6, 1912. 



^ Walcott : The Monarch of the Canadian Rockies, Nat. Geog. Mag., May, 1913. 



