(i) 14 



Palxontologia Sinica 



Ser. B 



These measurements clearly indicate the 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 calicnlum, but that it was very great is 

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

 the known length of nearly 90 mm. It is quite possible 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. Measurements at four successive points around the periphery 

 gave for three different specimens : 



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

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

 ances as characterize A. minganense, though scattered tubercles may have existed. 

 Comparisons. This species agrees with Archxocyathus minganense Billings in the 

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

 upon by Hinde (1889) though Billings' figures (1862, figs. 343-344) indicate its presence 

 (see also Roemer 1876, pi. II, fig. 2a, b). Because of the absence of the inner wall, Hinde 

 erected for this species the new genus Archxoscyphia. Hinde and subsequent authors (see 

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



