604 DESCBlPTiON OF {^Polygastriba. 



a slight difference in the form of the frustules, which are rather 

 shorter compared Avith their width, and are more truncated at their 

 extremities. 



ScHizoNEMA neglecticm (Thwaites.)— Tubules ramose, mucous ; na- 

 vicula; lanceolate, delicately striated. In brackish water near Bristol. 

 The filaments of this species are branched, especially towards the base, 

 and easily escape detection, owing to particles of sand and other 

 substances adhering to their tenacious surface, and being with 

 difiiculty removed from it. The frustules are very like those of 

 ^. floccosum, (Kiitz.) but the latter are not striated, and are included 

 in a gelatinous sheath of much greater thickness. 



At the conclusion of his description of the Schizonemece, Kiitzing 

 has appended the names of fifteen species, collected from various 

 authors which are doubtful, members of the genus ; for these we 

 must refer to that writer's monograph. 



Genus Stnctclia (Ehr.) — Envelope double ; inner one, or lorica, 

 siliceous, navicular ; external envelope amorphous, gelatinous. The 

 naviculse develope in clusters by self-fission, within the gelatinous 

 investment. Ehrenberg states, that there are two openings near the 

 middle, on one side, but they are indistinct. 



The following characters are from Kiitzing. 



" Individuals cymbelliform ; transversely connate, in curved cir- 

 cular bands (bundles), imbedded in a soft amorphous and gelatinous 

 siibstance." 



In Kiitzing' s arrangement, Syncyclia is one of the family 

 Cymhellece. 



S. quaternaria. — Corpuscles in pairs, or in fours, smooth, en- 

 veloped in a hyaline jelly, contents of a golden or reddish-brown 

 colour. Length 1 •864th. The frustules have the form of Cocconema 

 cistula, but are destitute of striae and pedicles. 



S. salpa. — Lorica semi.ovate, mostly connected in sixes within the 

 gelatinous substance, and so that on a ti'ansverse or end view they 

 appear like a group of corpuscles in the form of a ring. Colouring 

 matter green. Length l-2300th. to l-570th. ; group 206, showing 

 to the right a single frustule, several side views ; and below, an end 

 view of a ring-like cluster. 



This form occurs as a mucous film upon sea- weed. 



