NO. I CAMBRIAN FAUNAS OF EASTERN ASIA 67 



pyge [see Locality 35;-, p. 33] is found with Solenopleura, Anonio- 

 care, Dolichometopns, and other genera associated with Paradoxides 

 in the Atlantic Province. The order of stratigraphic succession of 

 the Dorypyge fauna is essentially the same in the two provinces. 



The Middle Cambrian fauna, like that of western North America, 

 is much larger and more abundant than that of the Upper Cambrian. 

 This was due in a considerable degree to the usually favorable con- 

 ditions existing on account of the great variety of habitat afforded 

 by the seas of the period. The advancing and deepening Middle 

 Cambrian sea forced the local faunas to change their habitat from 

 time to time and they had either to adjust themselves to the new 

 conditions and habitat or to perish. Local isolation for long periods 

 led to the development of new forms, and these, when the barriers 

 were removed, contested and competed for their position and exist- 

 ence with other faunas until, by a process of elimination of those 

 least fit to survive, the development was hastened of a large and 

 varied fauna. By the close of the Middle Cambrian more stable 

 conditions prevailed and the era of rapid evolution was checked 

 until, under the impulse of new conditions of environment and 

 accumulated tendency to change following the close of the Cambrian, 

 a great evolution of new forms of life began. 



Upper Cambrian fauna. — The geographic distribution of the for- 

 mations containing this fauna is the same as for the Middle Cam- 

 brian, so far as now known. In the Sin-t'ai district the upper shale 

 (Ku-shan?) and its fauna serve to form an upper horizon to the 

 Middle Cambrian. The first fauna above the Ku-shan shale occurs 

 in a limestone and, although only 10 feet (3 m.) higher in the sec- 

 tion, is entirely distinct from that of the Ku-shan shale. It includes 

 the following: 



Billingsella pumpcllyi (C61) Chuangia fragmcnta (C61) 



Proampyx burea (C61) Chuangia nitida (C 11) 



Pterocephalus busiris (C61) Ptychaspis baubo (C61) 



Chuangia batia (C 11, C33fl, C61) Anomocarella bcrgioni {Czza) 



Sixty feet (18 m.) above the Ku-shan shale the fauna includes: 



Chuangia batia (C 11, C2,2i(i) Anomocarella bergioni (€330) 



Chuangia nitida (C 11) 



In the Ch'ang-hia district, at about 100 to 120 feet (30 to 36 m.) 

 above the base of the formation, the fauna is relatively large and 

 varied. It includes the following: 



