(in) 12 Palxontologia Sinica Ser. B. 



Measurements : 



Greatest width = 13 mm 



Hinge line =10 ,, 



Height = 9 ,, 



Proportion of height to width = 1.44 



A second exterior impression of a Brachial valve (Ser. No. X 216 PI. I, Fig. 

 8a) is of a smaller specimen as compared with No. X 218. Its measurements are 

 as follows: 



Greatest width — 8 mm 



Hinge line =7 ,, 



Height =5 ,, 



Proportion of height to width = 1.60 



The sinal depression is very clear and the arrangement of the sinal plica- 

 tions is shown in Text-Figure 2. 



Text-Fig. 2. Arrangement of the sinal plications in specimen No. X 216. 



The sinal plications have increased to six instead of four. Bifurcations and 

 branchings of plications are in general more numerous than in the case of No. X 



218. 



A third exterior impression of the brachial valve (Ser. No. X 220, PI. I, Fig. 

 9a) has the following measurements: 

 Greatest width = 13 mm 

 Hinge line = 6 mm '. 



Height = 9 mm 



Proportion of height to width = 1.44 



Part of the hinge line is broken away, so its extent is in doubt. No. X 220 

 differs from No. X 218 in (1) the lesser prominence of the sinus, (2) more bifurca- 



