MICROSCOPICAL APPEARANCE OF THE VALVES OF DIATOMS. 221 
are difficult to those only who have failed to grasp the general 
organization of the diatom frustule. 
Fig. 48. 
g.p. Large flap (grand pan) 
pf. Small flap (petet par) 
gf. Interior portion of large flap reaching beyond 
the small flap (partze interieure du grand pan 
dépassant le petit pan ) 
c. Free edges of the hoop (dords bres du connectif) 
It may also be remarked that many Amphoree—just as is noticed 
in other genera—show hoops divided in a circular manner, so that 
Fig. 49. 
gp. Large flaps (grands 
pans ) 
&fj. Young large flaps 
(grands pans jeunes ) 
pp. Small flaps (fetzts 
pans) 
2’ .p. Young small flaps 
(petits pans jeunes ) 
7, Junction line of the 
smaller flaps, old and 
young (ligne de jonction 
des petits pans anciens et 
jeunes ) 
¢c.s. Outer hoop (connectif 
superior ) 
c.z. Inner hoop (connectif 
inferieur ) 
a. Central nodule (zodule 
central ) 
Cs cc 
they exhibit a series of fine multiple and parallel strice instead of a 
single siliceous ring attached to the edge of the valve, Certain 
, 
