EXPLANATION OF PLATES 219 



Isochilina armata Walcott var. pygmaea var. rvov. 



p. 72 



Fig. 



19 A somewhat fragmentary right valve showing a deep depres- 



sion in front of the spine, x 22 



20 A perfect right valve possessing a short unciform spine. 



x22 



21 A somewhat elongate * right valve with distinct cardinal 



mucros. x 22 



22 A small left valve possessing a long, straight spine and two 



faint depressions, x 22 



23 A very obese left valve with very strong anterior mucro. x 22 



24 The smallest valve observed; possesses long straight spine 



and distinct eye tubercle, x 22 



25 A left valve with 'broad depression and eye tubercle, x 22 

 Pehbles of groups 5 and 6 



Bythocypris cylindrica Hall sp. 



p. 87 



26 A left valve with a remarkable tumidity of the ventral region. 



x 22 

 27, 28 Two other specimens showing slight variations in outline 

 from the average examples, x 22 

 Pebbles of groups 5-7 



