(I) 14 



PaLrontoIof/ia Sinica 



Ser. B 



Rate of tapering 



1 in 2.:; 



1 in 



1 ill 2.« 



1 in 3. 57 



These measurements clearly indicate tlie gently tapering character of the calicu- 

 lum and the variation in the thickness of the wall or thecarium vertically. We have no 

 means at present of determining the length of the caliculum, hut that it was very great is 

 shown liy the fact, that in one of tliC specimens there is so little variation in diameters in 

 the known length of nearly 90 mm. It is c|uite possiltlo that this species grew to be over 

 30 cm. in length. 



There is considerable variation in the thickness of the wall around the periphery 

 as shown in the sections. i\L_'asuroments at four successivo i^jints around the periphery 

 gave for three different S[)ecimens: 



Section pi. 1 fig. o 



16 



S 



Si.'ition pi. 1 fig. 



Section pi. 1 fig. 1 



lu 



12 



!_) 

 10 



16 



15 

 20 



From the several sections it appears that the form was subcylindrical with the 

 surface of the thecarium scarcely undulating, nor did it exhil)it such marked protuber- 

 ances as cliaractei-ize A. miujjuiieiua, though scattered tulicreles may have existed. 



C(>mi>iii-lR(fm. This Sjx'cies agrees with ArrJifvoci/atlais minganense Billings in the 

 absence of the inner wall of the thecarium. Its absence in ^1. minganense has been insisted 

 upon by Hinde (1889) tliough Billings' figures (18(32, figs. 343-344) indicate its presence 

 (see also Roemer 1S76, pi. II, fig. 2a, b). Because of the absence of the inner M'all, Hinde 

 erected for tliis species tlie ne\\' genus Arehirrmijpliin. Hinde and subsequent authors (see 

 especially Taylor 1910) were in error in believing A. mrnijanrnxc to be a Cambrian 



