DI. \TOMA (!:.!: OF NORTH A: M HI MCA. 



< Valves not symmetrically divided by the raphe 



1. - Aiiniilicitt XVI. 



(. All others CCXVOXKIS xvn. 



TRIBE II. PSEUDO-RAPHIDIE.K. 



FAMILY VI. FI;A(;ILARIE.E. 



Frustules arcuate in f. v.. valves with interrupted 

 transverse striae or costae ; and one or both valves 

 with pseudo-nodules (blank spaces) at the ends. ... 



GEPHYRIA \\iii. 



[ Frustules and valves not as above 1 



I Frustules more or less arcuate in s. v., with trans- 

 verse (often granulate) ribs (canaliculi. W. /S. > : 

 1. which in f. v. frequently cause the margin or sub- 

 margin to appear beaded, or dentate EPITHEMIA xix. 



[ Frustules not as above 2 



Frustules arcuate in s. v. : not ribbed : valves trans- 

 versely striate, without median line or nodule, and 

 with pseudo-nodules at the ends, on concave mar- 

 gin EUNOTIA xx. 



[ Frustules not as above :> 



f Valves with a pseudo-raphe. and transverse rows of 

 o granules within square eells (clathrate); central 



and terminal nodules distinct GLYTIIODKSMIS xxi. 



Valves not as above 4 



Valves cruciform ; with interrupted transverse striae 

 (not clathrate'. central nodule very distinct. 

 4. ! Frustules in f. v., with terminal vittae:' 



<>>!l/>//<llOJ>Kix XXII. 



Valves not as above 5 



f Valves with central and terminal nodules (or blank 

 spaces), latter prominent in f. v. ; and pseudo- 

 median line (not always distinct > ; valves fre- 

 quently constricted or inflated at the middle: 



frustules cohering J>i(nlrsntit< xxm. 



t 'Valves not as above 6 



I Valves with a central (generally transverse) blank 

 space, and a central pseudo-ocellus : or with two 

 or more < few ) strong pervious costae in the middle, 

 which are prominent in f. v. ; and transverse 

 genera!l\ moniliform interrupted i striae or costae. 



or square cellules ; and terminal nodules 



I'LACHM; i; \ M.M A \ xiv. 

 YaKesnot as above 7 



