Navicidacea.'] infusorial animalcules. 3(59 



other margin is flat, with a projectiou iii the centre. In both fonns 

 the lateral surfaces are marked with close transverse striae. Mr. Ralfs 

 appears to regard fig. 171, as representing this variety. 



Feagilaria vireHccns (Ualfs.) — Frustules broad, with two evident 

 puncta at each end ; lateral siu'faccs turgid, lanceolate, constricted 

 near the ends ; striae none, or indistinct. Fresh water pools. Plant 

 green, not much altered in drying. The frustules frequently separate 

 and cohere by the angles in a zig-zag chain, from which circum- 

 stance it is doubtful whether the plant is rightly placed in this genus. 

 The frustules are often nearly square, but more frequently three to 

 four, or sometimes five to six, times longer than broad. The endo- 

 chrome is greenish, and consists of numerous small granules, either 

 scattered or collected together in the centre of the frustules. 



When the frustules adhere together by their angles, this plant 

 bears a considerable resemblance to young specimens of Diatoinavulgare, 

 from which, however, it may be distinguished by its green colour 

 when recent, by the form of the lateral surfaces, and by the apparent 

 absence of striae under a moderate power of the microscope. 



Mr. Ralfs considers this sjiecies = F. pectinaUs (E.) ; Kiitzing 

 tliirLks it = F. confervoides of Greville ; but the former says it is not, 

 for F. confervoides (Grev.) he haS^iscertained to be F. hyemalis. 



Genus Gallionella (Ehr.) = Mehsira (Agardh.) — Lorica bivalve, 

 cylindrical, globulai', or discoid, concatenated, chain free. The seg- 

 ments (frustules) have each one or two oblique furrows, with several 

 openings in them. The lorica, viewed end ways, is circular, re- 

 sembling a coin. It is fragile and incombustible ; that of G. ferni- 

 ginea (see description of this species and remarks) appears to be com- 

 posed of silicate of iron. A coloured and divided mass of granules 

 (ova, E.), clustered like grapes, is seen internaUj', as also colourless 

 vesicles. Change of place has not been seen. lu their concatenated 

 form, they closely resemble filamentous Algae. Nearly all the species 

 are found both fossil and living ; the fossil forms, especially, are 

 exquisite objects for the microscope, under a high power and proper 

 illumination. Living forms occiu' both in fresh and in salt water. 



Kiitzing' s definition difters from that of Ehrenberg, mainly in de- 

 scribing the filaments as adnate, or attached. Like Mr. Halt's, the 



