Structure of the Diatom Shell, &c. By Dr. J. D. Cox. 405 



minutes. Fimbriated rim with fracture through first row of 

 hexagons showing these in section. From Peticolas' sHde of 

 diatoms from Fernandina, Florida, in balsam. 



No. 101. Isthmia nervosa Kiitz. x 1180, exposure 10 

 minutes. Fragment of valve, showing dots around margin of 

 alveoli. From my own preparation of recent diatoms from 

 California, in balsam. 



No. 102. Same species, x 1220, exposure 12 minutes. Hoop, 

 showing vanishing film extending beyond the suture. From same 

 slide as last. 



No. 103. Same object, x 740, exposure 6 minutes. 



No. 106. Triceratitim favus Ehr. x 1150, exposure 12^ 

 minutes. Fragment, focused upon a plane through the process 

 and adjacent hexagons. From Peticolas' slide of diatoms from 

 Fernandina, Florida, in balsam. 



No. 107. Isthmia nervosa Kiitz. x 1100, exposure 10 

 minutes. Fragment of valve with unusually strong marking in 

 the alveoli. From Peticolas' shde of San Luis Obispo (California) 

 earth, in balsam. 



No. 108. Same object as the last, x 1100, exposure 10 

 minutes. Focused upon another part of the curved surface. 



