OF TIIK KAMI I. IKS AM) (ii;\KRA. ]! 



TRIBE III. CEYPTO-EAPHIDIB^E. 



Frustules cylindrical, or flattened, valves alike (ter- 



minated by a calyptra); pointed wit h a brist le ISA 



- Frustules not as above 1 



( Frustules with valves unlike, or mostly smooth ; and 



/ 



furnished with awns, horns (elongated processes', 

 spines, or setae, which are sometimes absent or 

 imperfect in fossil forms: frequently imperfect l\ 

 silicious. valve not ribbed radically, or cellulose... ISA 



I Frustules not as above 2 



I Frustules imperfectly silicious, connecting /one 

 2 more or less turgid ; connected in distant series; 



valve angular, with long central spine ISA 



L Frustules not as above... 3 



., ( Valves with a single pseudo-nodule ls<; 



( Valves not as above 4 



_j I Valves lunate, not transversely costate, or septate... ls<; 

 (. Valves not as above ." 



! Valves somewhat hispid: with sinuato-ivliculate 

 lines i not rayed) is,(i 

 Valves not as above.... i; 



f Valves circular or angular, not much developed in 

 (i f. v., with (obscurely) reticulate center, and con 



spicuous pore-like puncta ls(l 



Valves not as above 7 



f Valves alike, smooth (hyaline), with radiating lines 



. 



(linear rays not terminating in a spine); raysdefi- 



| nite (few; 18F 



Valves not as above S 



f Frustules cuneate in f. v.. or with decided ocelli, 

 s processes, or tubercles, generally few and promi- 

 nent in f. v. (not spines alone) 11 



Frustules not as above ! 



f Frustules cohering: generally much developed in 

 f. v.. and cylindrical: '.irmly silicious: valves 

 rarely hyaline, unlike, or elliptical : without me- 

 dian line; sometimes apiculate, or conical, or with 

 -, ., a peculiar central nodule (spine ; radi;i!e punc 

 tate. or cellulate; and frequenlly with mnrginal 

 or sub-marginal spines. Krustules cohering by 

 smooth sutui'al lines, r by marginal spines 01 

 teeth, or by a central spine.. . 1> S I> 



I Frustules and valves not as above lL' 



