54 



RESEARCH IN CHINA. 



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 conditions 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 them- 

 selves 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 existence 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 evolu- 

 tion 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 formations 

 containing this fauna is the same as for the Middle Cambrian, 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 section, is entirely distinct from that of the Ku-shan 



shale. In includes the following: 



Billingsella pumpellyi (C6i) 

 Proampyx burea (C6i) 

 Pterocephalus busiris (C6i) 

 Chuangia batia (Cn, 330, C6i) 



Chuangia fragmenta (C6i) 

 Chuangia nitida (Cn) 

 Ptychaspis baubo (C6i) 

 Anomocarella bergioni (0330) 



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



Chuangia balia (Cn, 330) Chuangia nitida (Cn) Anomocarella bergioni (0332) 



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: 



Obohis matinalis ? (054) 

 Obolus (Weslonia) sp. undt. (56) 

 Discinopsis sulcatus (Cs6) 

 Eoorthis pagoda (054, 056) 

 Syntrophia orthia (C 54, C 56) 

 Scenclla sp. undt. (Cs6) 

 Matherclla circe (C 56) 

 Pelagiella pagoda (Cs6) 

 Onlwtlieca sp. undt. (056) 

 Cyrtoceras cambria (Cs6) 

 Agnostus sp. undt. (034) 

 Conokephalina belus (Cs6) 

 Conokephalina dry ope (56) 

 Lisania sp. undt. 



Pterocephalus busiris (054) 



Pagodia bia (Cs6) 



Pagodia dolon (041) 



Pagodia lotos (56) 



Pagodia macedo (034) 



Afenoceplialus ? depressus (049,056) 



Ptychaspis brizo (038) 



Ptychaspis cadmus 



Ptychaspis calchas 



Ptychaspis calyce (042) 



Ptychaspis campe (042) 



Ptychaspis ccto (34, C 3 8, 54, C 5 6) 



Ptychaspis sp. undt. (54) 



Coosia carme (C 38) 



