402 ANIMAL NATURE OF DlATOMEjE. 



former, {notata, Martensiana, Vaucheria,) the form is so 

 similar to that of Navicula as to leave nothing but the 

 want of central aperture to distinguish them. "Finally, 

 there are not wanting in this section species more or less 

 curved. Those that are curved in the secondary surfaces 

 {mesolepta, biceps^ might be regarded as similar to 

 Eunoiice, but they differ essentially in being attached. 

 Those again which are curved in the primary surfaces 

 {Ulna, tergestina, armoricana, sigmoidea, vermiculans,) 

 have analogy only with the Achnanthese. As to the 

 Sigma, Kiitzing himself avows his suspicion that it may 

 belong to the Baphidogloece. 



**** Tabularia ; bacillis in stipite brevi, liorizontaliter 

 crescente, tabulatim disruptis. 



Exclusive of two {S. Gallionii, S. Arcus,) all the spe- 

 cies (9) of this section want the transverse striae ; and all 

 have that linear form, slightly attenuated at the ex- 

 tremities of the primary surfaces, which we have noticed 

 in many species of the preceding section. The distinctive 

 character of this section, the stipes on which the frustules 

 grow side by side contiguous to each other, is very im- 

 portant in an organographical point of view. And by 

 this character the species described and figured by 

 Hassall under the name of 8. lunaris would seem to 

 be related to the S. Arcus, if it be really distinct. 



***** Grallatoria ; stipite elongato smpe ramoso, ba- 

 cillis plemmque geminatis Icevibus. 



Among the six species of this section, which in their 

 aspect call strongly to mind the family of Licraophorese, 

 two are perfectly linear on the primary surfaces, (*S'. 

 crystallina, 8. gigantea,) and one of them {giganted) has 

 the extremities of the secondary surfaces capitate. The 

 rest have the primary surfaces attenuato-truncate at the 

 extremities. All are smooth, wanting striae. 



