P. T. Cleve: The Diatoms of Finland. 17 



and R. Bolleana. The former may perhaps be united with the 

 complexse (Nav. rhombica), the latter is closely connected with the 

 radiosae. 



The genus Alloioneis is entirely unnatural and contains wi- 

 dely different forms. Alloioneis Antillarum and A. Kurzii be- 

 long to Trachyneis (Nav. aspera group). A. curvinervia belongs 

 to the formosae. A. Grundleri is an isolated form, remarkable 

 for the peculiar form of the enclfissures, and seems to form a 

 transition to some Amphorae. 



The genus Stauroneis comprises several forms, which may 

 be more naturally classed among the Navicular, as St. ventricosa, 

 which belongs to the punctatae, and St. platystoma, which may 

 be classed either among the punctata? or the radiosae. The trans- 

 versely dilated central nodule is a character of no generic value, 

 as it occurs in widely different groups, as in Trachyneis and lyrae 

 (N. Oswaldii var.) The true Stauroneis-forms have fine, distinctly 

 punctate, more or less radiant striee and seem to be connected 

 with the group of clecipientes (Nav. crucicula etc.), which perhaps 

 is allied to the complexce (N. rhombica). 



The genus Cymbella is closely connected by many forms 

 with the punctata and the radiosce. Cymb. Frieseana Grun. and 

 C. Brasiliensis CI. are more nearly akin to the decipientes than 

 to the Cymbellae and may be separated from the true Cymbellae. 



With the Cymbellae some forms of the large genus Amphora 

 are nearly connected, so nearly indeed, that it is difficult to de- 

 cide in which genus they may be most conveniantly classed. But 

 Amphora comprises such widely different forms, that the whole 

 genus seems to be unnatural. Some Amphorae are evidently (A. 

 acuta etc.) nearly allied to Stauroneis, other to the complexae- 

 group of Navicula (A. obtusa etc). Some forms approach to am- 

 phiprora (Amporopsis, Auricula). In several Amphorae the structure 

 of the valve is nearly the same as in the genus Diploneis. Jt is 

 thus evident that the genus Amphora should be split up in diffe- 

 rent, genera, which might be classed in accordance with the sym- 

 metric naviculoid forms. 



The genus Gomphonema seems to come near to Cymbella. 

 Achnanthes comprises too manv different forms to constitute a 



