Vol I. 



Grahau — Orclovician Fomls from Xortli China 



(I) 13 



mostly continuous, very thin, and slightly serrate. They form a pronounced contrast 

 with the inner portions of the septa which, in section, are discontinuous. Occasionally 

 two of the outer septa become confluent. 



The following are the measurements of this section: — 



Longer diameter, exterior 30 mm. 



,, ,, interior 13 ,, 



Thickness of thecarium IG ,, 



Thickness on opposite side 7 ,, 



Transverse diameter, exterior 28 ,, 



,, ,, interior 11 ,, 



Thickness (if thecarium 8 ,, 



Thickness on opposite side ,, 



A specimen (Plate I, fig. 2), which evidently has boon compressed laterally, has 

 a present maximum diameter on the exposed weathered surface of 80 mm., -while the 

 shorter diameter is 40 mm. A series of sections -cut across this caliculum 25, 27 and 80 

 mm. from the exposed surface, and parallel to it, shows so little difference in measure- 

 ments that we must infer that the caliculum, in this part at least, was suhcylindrical. 

 These facts are brought out by a comparison of the following measurements. (Section 

 No. 4 is nearest the top of the caliculum). 



If the tapering was fairly uniform the length of the specimen must have been 

 between 35 and 40 centimeters; actually it was probaljly about half that. 



A third specimen, the largest ol.itained (Plate I fig. 1.) shows the following 

 measurements on the exposed ^\•eathered surface and in a section 50 mm. below this and 

 parallel to it. The total length was probably 20 cm. or over. 



' ) In last part only. 



