Biatomaceas from the Caspian Sea. By A. Grunoiv. 691 



be convinced of the correctness of this view. PI. XXI., Fig. 5 a,b 

 Ci°)i Cydotella scotica Kg. from Scotland ; 5c C\^), structure of 

 valve. 



In a future paper I hope to give delineations of some forms 

 of H. Isevis Ehr., H. radiatus \Pyxidicula radiata O'Meara), 

 and H. maximus Petit. 



