Naviculacea.'] infusoriai animalcules. 499 



mucous, 'and fragile, sparingly branched ; naviculae truncate, loosely 

 distributed in iudefinite lines. In length l-1380th. 



^ca.izoiSTiUk.'tenuis8imum. — A compact, mucous, brown, and densely 

 intricate stratum, with crisp, subramose tubes, very slender, hyaline, 

 and fragile ; naviculse very small, obsoletcly striated, linear, and trun- 

 cate. Length l-1320th. 



S. llhjrkum. — In a mucous stratum, inti'icate, of a dull and obscure 

 gx'een colour ; the tubes (coelomata) very slender, simple (?), very 

 delicate and hyaline ; naviculae acuminate, lanceolate, in dense rows ; 

 when dried, not distinct. Length l-1680th to M440th. On 

 Conferva, in brackish- water. 



S. tenue. — In an interwoven dense stratum, of a brownish golden 

 colour ; the tubes almost simple, unequal, often contracted, hyaline ; 

 naviculae in indistinct rows, oftentimes without regularity in dis- 

 position, oblong, linear, and truncate in form. Length 1-1 200th. 



S. lutescens. — Tufted, imdulating, glossy; of a pale reddish colour 

 when dried ; coelomata almost simple, capillary, coloured and naked at 

 the base ; hyaline, and covered with naviculae at the apex ; naviculae 

 oblong, lanceolate, obtuse. In length 1-1 200th. 



S. ruUlans. — Tufted, imdulating, of a deep, shining, chestnut 

 colour, green at the apex ; tubes nearly simple at the base, brown 

 and bare ; at the apex hyaline and covered ; capillary ; naviculte 

 agglomerate near the apices ; oblong, linear, and truncate. In 

 length 1-1 200th. 



Var. fa. J S. parvulum. — Densely tufted, of a dull and opaque 

 green coloiu' ; naviculae remote, scattered, without regularity, slender, 

 and linear. Frond l-6th to l-4th. 



Var. fb.J S. Luhricum. — Tufted, green, with crystalline tubes ; 

 with hyaline and particularly mucous branches at the apex ; navi- 

 culae rather larger, wide, and very distinct. Length 1-1 080th. 



Var. fc.J S. Hoffnianni. — Tufted ; pale green at the base ; brown- 

 ish at the apex ; crisp tubes, hyaline (not coloui'ed) ; naviculae close, 

 very distinct, oblong, widely truncate, and on the other side lanceolate. 

 In length 1 -960th to l-1080th. 



Var. (d.) viride =^ S. haltimm (Ehr.) — Tufted, green ; coelomata, 

 hyaline, colourless ; naviculae slender, linear-lanceolate, obtuse. 

 In length l-1200th. 



