446 ANIMAL NATURK OF DIATOME/E. 



breadth, both of the perfectly linear primary, and the 

 elliptico-elongate secondary surfaces is about 0*008. *Wjz 

 shall find a perfect agreement with Kiitzing's figure by 

 supposing, as usual, that it represents one half of the 

 indicated amplification of 420 diameters, the Naviculae 

 being here 8*5 millim. long. 



I believe that some specimens, also collected at Trieste, 

 by Zanardini, (which are perfectly similar to the preceding 

 in external appearance, but of which the Naviculse are 

 shorter and more slender,) belong to a different species, 

 not described by Kiitzing. In the one, the length is five 

 times the breadth ; in the other it is six times in respect 

 to the secondary surfaces, and more than eleven times in 

 respect to the primary. Length 0*036; breadth of the 

 primary surfaces 0'006, of the secondary, 0-0035 millim. 



Sckizonema corniculatum, Ag., (Micromega.) 



Although I might be supported by Kiitzing in the 

 determination of this species, and though my specimens 

 perfectly agree in external appearance with the figure 

 given by this author, still I cannot but confess some 

 doubts as to the species itself. And, in the first place, 

 Kiitzing attributes a larger size to the Navicula3 than to 

 those of the preceding species. He says they are no less 

 than ^th of a line, therefore 0'054 millim., and in con- 

 formity to this he represents them 1*1 millim., with an 

 amplification one half less than what he assigns to his figure. 

 On thfrother hand, I find the greatest length 0'03, and the 

 greatest breadth, whether of the exactly linear primary 

 surfaces, or of the elliptico-elongate secondary, 0'007. 

 The length being rather more than four times the breadth, 

 the form of these Naviculae corresponds with that re- 

 presented by Agardh (Icon. Alg. l?urop.,tab. 4.) I find 

 that the figure given by Agardh himself does not corres- 

 pond with it in external appearance; the figure agrees 

 much better with the preceding species. 



It is true that we can find this form more or less rich 



