JVavicidacea^] infusorial animalcules. 34S 



and ventral hook in the middle of the sides, and two apertures at 

 the angles. 



Denticella (?) tumida. — Testules turgid (subglobose) without lobes 

 or septa ; surface minutely dotted ; with two long exserted (projecting) 

 tubules and seta) on each side. Diameter 1 -960th. Bermuda. 



D. lavis. — Has the habit of D. aurita, but with a smooth triden^ 

 tate testa. Diameter 1-4 32nd. Antarctic Sea. 



D. Biddulphia. — Sculptured. In habit and surface resembles Bid^ 

 diilphia piilcliella, but has long setae disposed midway between the 

 contiguous halves. It has three cells, and two septa to each lateral 

 segment. (P. 13, f. 48.) Cuba, Peru. 



D. Rhombus. — Surface, with very minutely dotted lines : resem- 

 bles Zygoceros Rhomhus, but is provided on each side, at the middle, 

 with a sharp hook. Diameter 1-3 12th. Petersburg, Virginia. 



The band (zone) on the dorsum, like as in Zygoceros, is not smooth, 

 but adorned with rows of minute dots (puncta.) 



D. tridentata. — ^Has the habit of Biddulphia tridentata, but the 

 di.z\\\.Gioi a. Denticella. Diameter l-480th. Yirginia and Maryland. 



D. (?) pohjmera. — Testules very broad, with ten to twelve septa 

 and lobes ; siu-face granular ; six granules on the anterior surface of 

 tht' central lobe, disposed in the for^^'/f a star ; spiny denticles on the 

 sides, not in the median line ; tubules of the apertures projecting 

 some distance. Length 1-1 32nd. Bermuda. 



Genus Denticula, (Kiitz.) — Free, solitary, or binate; linear- 

 oblong on the primary side ; the secondaiy transversely striated 

 or costate ; strire very distinct. 



This genus, named by Kiitzing, is placed in the family Fragila/riea, 

 Its members known to Ehrenberg, were described by him, some 

 among Fragilaria, others with Bacillaria, (Biatoma). Benticula 

 approaches Surirella and Navicula. 



D. tenuis. — Narrowly linear, margin finely punctate ; secondary 

 side minutely striated, narrowly lanceolate; transverse strite ten 

 to eleven in l-1200th. Length l-1080th. Among Conferva at 

 Nordhauscn. 



D. frigida. — Oblong, small, margin finely striated ; secondary side 

 linear lanceolate; transverse striae eleven to twelve in l-1200tll/ 

 Length 1-1 200th, Cold Alpine streams, Thun, Switzerland. 



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