AET. 9 XEW CAMBRIAN CRUSTACEA — RESSER 5 



definitely indicated, but since the lower part of the Burton forma- 

 tion outcropping nearby apparently contains a fauna of similar age, 

 while the upper portion contains the Middle Cambrian Albertella 

 fauna, it becomes apparent that here the upper Mount Whyte, 

 {Kochiella fauna), ^ is absent. 



The rare Pennsylvania fossils herein described or referred to 

 are all in the Kinzers formation,* which has the typical Mesonacid 

 fauna that is comparable with the Eager formation just mentioned. 

 Beside the Tuzo'ia^ Ano^nalocaris^ and merostome described from this 

 formation in this paper several other unusual fossils have been found, 

 including notably a sponge and a species of some Holothurian pos- 

 sibly belonging to the genus Peytonia. Both the eastern and western 

 Mesonacid faunas have now furnished such fossils that clearly show 

 that the Burgess shale fauna was derived from the same ocean. 



Several other Lower Cambrian collections from western North 

 America, made in fine grained argillaceous rocks that break with 

 sufficiently large smooth surfaces to preserve them, give us speci- 

 mens of phyllopods, among which such genera as Hwdia^ Hymeno- 

 caris, Isoyxs, together with several new ones, are represented or sug- 

 gested. In eastern Yun-nan, southern China, Mansuy ^ has found 

 several phyllopods in the Redlichia beds, quite similar to those from 

 the western American Mesonacis bearing beds, and in addition a 

 merostome that he described as Amiella pHsca. Thus it will be 

 seen that many of the " lower " Crustacea as well as algae, sponges, 

 jellyfish, and worms were already important in the Lower Cambrian 

 seas, and if we should ever be so fortunate as to find another Burgess 

 shale preservation in these older rocks we may expect a great array 

 of organisms. It will also be observed that indications point to the 

 direct descent of the Burgess shale fauna from these older Mesonacid 

 assemblages. It might be added that certain trilobites in the Eager 

 beds seem to belong somewhere between the Mesonacidae and such 

 Middle Cambrian forms as Zacanthoides. 



All the faunas here discussed, both the Lower and Middle Cam- 

 brian, lived in epicontinental seas whose waters were apparently 

 extensions of the Arctic Ocean. 



BIOLOGICAL RELATIONS OF THE FOSSILS 



Knowing very little about the structure and systematic relations 

 of the Crustacea, I hesitate to say anything in this connection regard- 

 ing the biological significance or relationships of the fossils pre- 

 sented in this paper, but a few general observations may be in order. 



s Walcott, 1917, Smithsonian Misc. Coll., vol. 67, no. 3, p. 63. The Mount Whyte hag 

 a Mesonacid fauna in its lower part and the zone with Olenopsis (=Kochiella) agnesensia 

 in the upper. 



* Stose and Jonas, 1922, Joum. Washington Acad. Sci., vol. 12, no. 15, p. 359. 



6 Mansuy, 1912, Mem. Serv. Geol. L'Indochine, vol. 1, fasc. 2. 



