396 ANIMAL NATURE OK DTATOMEiE. 



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 strise on the primary surfaces. 



16. SuRiRELLA. — Individua singularia navicularia, 

 margine striata ; latus secundarium primario majus, linea 

 media longitiidinali Imvi percursum. 



This genus is divided into four distinct sections. The 

 first comprises the flexuose species, {8. clgpeus, S. Cam- 

 pilodisciis, 8. jlexuosa, 8. elegans, 8. spiralis, 8. Myodon) ; 

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

 induce Kiitzing to separate these generically from Cam- 

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

 the above-mentioned character of strias continued over the 

 primary surfaces in Catnpylodiscus 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 8urirellce. 



In the 8. Campylodisciis Kiitzing represents (PI. xxviii, 

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

 perfect figure of a Campylodiscus, and their inclined 

 mai'gins viewed in front [a, b,) resemble transverse striae 

 on the primary surfaces. 



The species [8. didyma, 8. solea, 8. regula, 8. multi- 



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



the extremities of their lateral surfaces {medio plerumque 



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



