234 CONTRIBUTIONS FBOM Mil NATIONAL rTERBABITJM. 



Subfamily II. pennatae. Valve do! neutrally built; that ia, not arranged in 

 relation to a centra] point orfocua, but rather to a median line; outline gener- 

 ally boat-ehaped or rod-shaped, sometimes oval, cuneat at-shaped, 

 irmoid; markings generally pin ti:» t . or transverse (imperfectly radiate in 

 som< iropylodiscus . true raphe, or hyaline median line pseud- 

 ured by latere] wrings or keel cryptoraphe always 

 present pines, etc. uncommon. 

 \ No true raphe; a hyaline median line (pseudoraphe) jnresent, rarely obscure. 



I'i: \<.n \i:i.iii-i \ i 



a. Frustules united to forma ribbon or zigzag chain; outline in Bona] view 



rectilinear; zone generally composed of separate bands; valve long-oval 

 or lanceolate. T\ bei i \kii u 



a. Prustule in zonal view unbent; valves not concave and convex. 



T \ m i I \ i:i!\ \ I 



Valve transversely partitioned by interna] vertical septa; that is, 



perpendicular to zone in zona] view DetUtculc p. 318 



Valve uot transversely partitioned (may !>•■ transversely undulate, 

 species of Grammatophora ; interna] septa parallel to zone in 

 zona] \ iew. 



LnternaJ septa massive, generally undulate, approaching from 

 either end of the frustule toward but not to the center, lea> ing 

 a oonseptate central space which appears in valval vi< 

 centra] ova] in each valve; zone hyaline or longitudinally 



dotted Grammatophora p. 319 



[nternal septa delicate, discontinuous, not undulate, inter- 

 rupted at three or more places, the uonseptate spaces app< ar- 

 ing in valval view as bo many ovals along the valve; zone or 

 zonal bands transversely marked TesseUa p. 321 1. 



b. Frustule in zona] view bent; one valve concave, the other convex. 



Entopi UNA] 



Valve transversely ribbed, the ribs on one aide of the median line 

 alterhat ing with those on the other side, the median line therefore 

 zigzag; internal septa on each Bide of the valve pierced with oval 

 openings set in a straighl row parallel to and Dear margins of the 

 \ alve Entopyla p. 323 . 



Valve transversely ribbed, the ribs on one side of the median line 

 continuous with those on the other side, the median line therefore 

 straight; internal septa on each Bide of the valve pierced with 

 oval openings set in a zigzag row parallel to bul distant from the 

 margins of the valve Gephyria I p. 32 1 . 



b. Frustule solitary, or united into a fan or forming a spiral band; not forming a 



ribbon or zigzag chain; outline in zonal view rod-shaped <>r wedge- 



Bhaped; \ al\ «■ club-shaped. (Meridioneae.) 



Z<>nc composed <>t separate bands; internal septa pierced by a row of 

 Large <>\ al openings which in \ alval \ iew L r i\ r e a stepladder appearance 

 i<» the club-shaped valve ( 'limacosph nia p 



c. Frustules united to forma ribbon or zigzag chain; zone nol composed of 



Beparate bands. Fa \<.n. \ i.-i i \ i 



a. Valve with trans> erse septa. (Diatominae)... Plagiogramma (p. 325 



b. Valve withoul transverse septa. (Fragelariinae 



Dirru regramma l p 

 B. Frustule having one valve with true raphe, the other with distinct or obscure 

 hyaline median line pseudoraphe). ^chnanthoidi \i 

 i Frustule in zonal view bent, one valve concave, the other convex; outline 



of valve long-oval or boat-shaped. \< n\ wnn eae .Achnanthei p 

 1). Frustule in zonal > i«\\ straight ; outline of valve broad-ova] or nearly round, 

 coneideae < 'occont is 1 1». 328). 



