392 ANIMAL NATURE OF DIATOME^E. 



corresponding to an external furrow, bounds the ring itself 

 on both sides, and is easily discernible, also, from the 

 diminished thickness of the wall. Where this ring is 

 most dilated, it presents two fine circular striae, which 

 divide it into three bands, the central one being the 

 narrowest. In the longer articulations this central band 

 is as broad as the others, or broader, and finally there 

 appears a third circular line, and a corresponding dia- 

 phragm, which divides it. The wall of the two bands 

 resulting from the division of the central one, grows 

 thicker, and these become similar in every respect to the 

 lateral valves of the two contiguous articulations. But 

 no sooner are the two articulations complete, than they 

 detach themselves from one another, and nothing remains 

 to connect them but a lateral isthmus, in appearance like 

 a joint (forme apparente de cerniera] (hinge), as in 

 Diatomte and Grammatophorte. The internal substance, 

 in dried specimens, is in the form of spherules, adhering 

 tenaciously to the internal wall of the secondary surfaces ; 

 and one row only of these spherules adheres also to the 

 interstitial ring by the side of the canal, in a similar 

 manner to the teeth of the M. sulcata. Only whilst the 

 two articulations are being completed, these globules are 

 found in the intermediate space. On one occasion I 

 have seen an articulation inflated as in M. varians. The 

 isthmus is indistinctly unilateral and alternate. 



At first sight of this singular Diatomean, the mind 

 instantly recurs to the figure of the Odontella ; and this 

 resemblance is more strongly suggested by the figure 

 given by Bailey of his Gattionella, (pi. 11, fig. 8,) which 

 Kiitzing refers to Odontella polymorplia, a figure which, 

 except for the contraction corresponding with the circular 

 canals, coincides perfectly with our species. Were it. 

 only that Bailey, when comparing his Gallionetta with 

 Diatoma auritum, insists upon its cylindrical form, its 

 want of appendages, and the mode of connecting the 

 articulations by a "flexible hinge-like ligament," I 

 believe that Bailey might with justice regard his species 



