396 ANIMAL NATURE OF DIATOME.E. 



were continued through the entire depth of a cylinder 

 which I could only see obliquely or in front. 



As to the interruption of the radii, which is regarded 

 as a specific character, this is not at all constant, and 

 may, perhaps, depend upon the imperfect state of the 

 specimens. The dotted appearance of the central disc 

 always presents that regularity which Kiitzing only 

 represented in the fig. 5 before mentioned. Similar puncta 

 may also be seen in the spaces between the radii. The 

 central aperture described by Ehrenberg is rightly denied 

 by Kiitzing. A sort of analogy in form connects this 

 genus with some species of the next ; the only distinc- 

 tion I believe to be a repetition of that very important 

 character of transverse striae on the primary surfaces. 



16. SURIRELLA. Indwidua singularia navicularia, 

 margins striata ; latus secundarium primario majus, linea 

 media longitudinali Icevi percursum. 



This genus is divided into four distinct sections. The 

 first comprises the flexuose species, (S. clypeus, 8. Cam- 

 pilodiscus, S. flexuosa, S. elegans, S. spiralis, S. Myodori) ; 

 and really one is at a loss to find the motive that could 

 induce Kiitzing to separate these genetically from Cam- 

 pylodisci. In fact there only remains, in my opinion, 

 the above-mentioned character of striae continued over the 

 primary surfaces in Campylodiscus clypeus to distinguish 

 that genus. But the doubt already expressed as to this 

 character, acquires still greater weight when we compare 

 these Campylodisci with the flexuose Surirettce. 



In the S. Campylodiscus Kiitzing represents (PI. xxviii, 

 fig. 26, c, d,} the lateral valves detached, which give a 

 perfect figure of a Campylodiscus, and their inclined 

 margins viewed in front (#, d,} resemble transverse striae 

 on the primary surfaces. 



The species (S. didyma, S. solea, S. regula, S. multi- 

 fasciata, 8. thermalis,} narrower in the centre than at 

 the extremities of their lateral surfaces (media plerumque 

 constrictdB) are, in the opinion of Kiitzing himself, so 



