Naviculucea.'] infusorial ammauulks. 44.) 



central is some\vhat tiie largest ; approaches Graminaioj^horu undulata. 

 Fossil in Ireland. 



Tabellaria sculpta = Diadesmis sci(Jj)fa (Kutz.) — llescmbles Fin- 

 nularia Borealis, but is sometimes to be met AA'ith combined in fours. 



T. rohusta. — Testule thick ; length three times greater than the 

 breadth ; Avidely capitate on each side ; centre widely gibbose, with 

 subacute capituli. Length 1 -864th. Fossil in Connecticut. 



T. trinodis =: JVavicuIa (?) trinodis. — Linear, elongate, presenting 

 three undulations, the middle of which is the chief; on the sides, in- 

 flated. Fossil in Sweden and Ireland. Length l-860th to l-480th. 



T. (?) amphicephala . — Very small, much dilated at the middle; 

 apices capitate. Length 1-1 728th. Has the habit of Bihlarimn 

 Follis, but Avith thickened apices. Mountain meal of San Fiore. 



T. Bacillum (Ehi-.) 



T. davata. (Ehr.) 



T. undulata (Ehr.) 



The genus Tabellaria of Kiitzing contains the following species 

 not occurring in Ehrenberg's enilmeration, being either actually new 

 or otherwise differently placed and named. 



T. fioccuhsa = Bacillaria Tabellaria, and Navicida and Tabellaria 

 trinodis (Ehr.) (P. 16, f. 29.) 



T. ventricosa. — Joints tabulate, vittae alternate on the sides (end 

 view), much inflated in ventricose maimer. Length 1 -960th. In 

 Freshwater. Falaise. (P. 16, f. 26.) 



T. fenestrata. — Joints oblong, vittae opposite ; laterally, inflated 

 equally at the middle and at the two ends. Length 1 -600th to 

 1 -280th. In ponds and streams. England, France, &c. This 

 species not improbably = Tabellaria nodosa (Ehr.) Frustules four 

 times or more longer than broad. 



T. marinum (Lyngb. and Ralfs.) =; Tessella inter rupta (Ehr.) — 

 Frustules vaiying from nearly square to six times as long as broad ; 

 canal not inflated ; striae two. Dark brown when recent, greenish 

 when diy. Common or marine Alga3. 



" The mucous substance which forms the connecting medium 

 between the angles of the frustules is more developed in this than in 

 the other species." 



