278 ACHNANTHKS. 



ANALYSIS OF SPECIES. 



I. Valves with costce, between which are two rows of 



small beads . . . . .a. longipes. 



2. Valves beaded, without costa'. 

 * Lower valve with a stauros. 



Upper 



valve 



with 



raphe 



usually 



f Valve with cuneate apices 



A. trrevipes. 



Valve 



with 



apices 



f Valve constricted only at the 



Valve median portion, with apices 



constricted, j very slightly obtuse-round- 



al least / ed . . . A. subsessilis. 



1 



centric, obtuse- 



flexed. I rounded. 



at the 

 median 

 portion. 



I Valve constricted in the middle 

 and just before the apices 

 (_ which are truncate-rounded . A. coarctata. 



i Valve not constricted, regularly elliptic very 



^ small . . .A. parvula. 



Upper f 



valve j Valve linear sub-elliptic ; median striae shortened . A. Hungarica. 



with J 



raphe ; 



eccentric, | Valve linear-lanceolate ; all the striae of equal length . A. aftinis 



straight. ^ 



** Lower valve without stauros. 



a. UPPER VALVE ONLY DIFFERING FROM THE LOWER RY THE ABSENCE 



OF RAPHE AND NODULES. 



Valves ( 



broadly | Apices sub-acute ; striae very robust 



lanceolate -\ 



or elliptic | Apices obtuse ; stria? delicate 

 lanceolate. ^ 



A. delicatula. 

 A. Biasolettiana. 



Valve 

 narrowly 

 lanceolate 

 or linear. 



I Valve with capitate apices . . . A. microcephala. 



f Central nodule surrounded by a hyaline 



Valves area A - exUiS - 



w . j Central f Strias parallel ; apices obtuse . A. linearis. 



' nodule 



not 

 capitate 



I 



without -I Median striae somewhat ra- 



hyaline diate ; apices somewhat 



area. I rostrate . . .A. minutissima. 



[. Valve longly elliptic, inflated in the middle and at the apices 



A. trinodiR. 



b. UPPER VALVE DIFFERING FROM THE LOWER BY THE 

 PRESENCE ON ONE OF ITS MARGINS OF A HYALINE 

 SPACE IN THE FORM OF A HORSE SHOE . . A. lanceolata. 



