422 ANIMAL NATURE OF DIATOME.E. 



results a decided analogy to the Epitkemia, whilst the 

 resemblance to the Achnanthese, observed by Ehrenberg, 

 is not apparent ; and I said to the Epithemia rather than 

 the Cymbellea3 because neither Ehrenberg nor Kiitzing 

 take any notice of a median aperture on the lateral 

 surfaces ; with this we are not to confound the umbilicus 

 projecting from the ventral surface. 



34. STAURONEIS. Individua libera, singularia, navi- 

 cularia; apertura media transversali. 



The numerous species (34) of this genus, divided into 

 three sections laves, (genuina^ punctatce (Stictoneix) 

 striatfB (Stauroptera) do not differ from Navicula except 

 by the transverse direction of the aperture, a condition 

 on whose organographical value we cannot pronounce 

 any judgment, not knowing the office of this aperture, 

 nor its relation to internal structure. Still it is right to 

 observe that in many species it does not seem to be the 

 aperture itself that is placed transversely, but rather the 

 depression, at the bottom of which is found a round 

 perforation, as in Navicula, and, as in these, there is a 

 sort of funnel stretching into the cavity, which becomes 

 visible when we look in front of the primary surface. 



35. AMPHIPRORA. Individua libera, singularia, aper- 

 turis terminalibus binis mediis, nee marginalibus. 



From the figures of two out of three species, which 

 Kiitzing describes in this genus, it appears to me that 

 we may believe the two terminal apertures constituting 

 the essential character of this genus, to be nothing more 

 than the usual minute foramina which serve to terminate 

 the two longitudinal lines or canals that traverse the 

 primary surfaces of almost all Navicults. Nor perhaps 

 are central apertures wanting in the lateral surfaces; 

 but these are seen in profile in the figures referred to. 

 The so-called wings, (alee) or projections, belong, therefore, 

 to the secondary surfaces, and constitute the only dis- 

 tinctive character of the Amphiprora. 



