I ONTBIBUTIONS PROM nil. NATIONAL HERBARIUM. 



I>. \.il\-- circular, divided int. ► complete or incomplete radiating 



vride hyaline limbs; n<> horns of prominent spines, \« n\<>- 



DISM l 



(/. Yal\ •• partly or fully divided into sectors by radiating ridges running 

 from the margin toward or i < ► tin- center; marking strong; margin 

 massivel) sculptured; do process at the marginal end of the 

 dividing ridges; sectors all on one plane. Stu roDisciNAi 



Valvi Hat or aearl) bo; radial ridges many, the main 



ones reaching the generallj rosetted center; mon 

 united to each other by concentric crose Lin< b, thereby gi 

 a Bpider-web Bculpturing to the valve; outline oi valve 



uniformly circular Hemiptychus p < 



Valve Burface often elevated at the center, i 

 tule more so than the other; radial ridges gent rally few, rarely 

 reaching the < <ni < •!•. which is without a rosette; do del 

 concentric lines forming a spider-web pattern, though a shad- 

 owy reticulation is sometimes present. Outline "i" valve 

 si imet imea p >lyg< >nal Stictodisc\ 



b. Valve divided into sharpl) distinct sectors !»> radial ridges uni- 



formly running from the margin to the hyaline central area; small 

 but evident -pine- usually at the marginal ends ol these dividing 

 ridges; alternate sectors generally depressed; that is, sectors in 

 two planes I Actinopty< hinae) Ictinoptycki 



c. Valve sharply divided into sectors by broad hyaline bars or Limbs 



running from a hyaline center toward or to the margin, their outer 



end- marked with a minute wart or Bpine; the hyaline center 



divided into more or less wedge-shaped divisions confluent with 



the limbs; spaces between the radiating Limbs marked with fine 



but closely Bel beading, arranged in radial or decussating order. 



(As'i i:i:<>i..\Mi'i:i\ \ ; 



Radiating Limbs all of the same width and generally tapering t<> 



the margin; central area either reticulated or divided by 



Btraight line.- into the same Dumber of parts as the limbs. 



Aaterolampra (p. 2 

 One of the radiating limbs narrowerthan the others; Limbs net 

 tapering t<> the margin; central area oever reticulated; une- 

 qually divided into the same Dumber of parte as the limbs by 



zigzag lines isteromphalv* p - 



<•. Valve circular; Burface imperfectly divided into sectors by alternate undu 

 Lating elevations and depressions, which are highest and Lowest at the 

 margin and decrease or disappear toward tin- center: each elevation 

 uingat it- highest poinl a blunt oipple-like horn, pointing radially 



outward and upward. Tripodisceae Tripodiscus I p. -77 i. 



d. Valve circular <>r round elliptical, surface marked with two rarely more or 

 only one) Large opposite Bubmarginal ocellae or ringed eyes, Blightlyor 

 considerably elevated above the plane of the valve; valve inarkii 

 beading, Lines, or both, arranged symmetrically with reference to the 



ocellae. Aulibcbai iuliscut p.281 . 



B. Valve oval or circular; frustule Long-cylindrical, the zonal diameter much ex- 

 ceeding the valval; /one made up of a series of rings or imbricated hands, 

 without internal septa ; frustules united into chains by their valves. (Soi i n- 

 oini 

 Valve in the form of a tall, tapering cone, it- apex excentrically placed 

 and tipped with a Btout, sometimes \ cry Long, hollow bristle or spine. 



Rkizo8olenia i,p. 2b3j. 





