NEW FORMS OF MARINE DIATOMACE^. 517 



phorae, the inner compartments seem to be in a different plane from the outer 

 ones. This species exhibits two frequent varieties, both smaller than the typical 

 form, which are figured (figs. 80 b, and 80 c). One is long and narrow, its length 

 being 0-0032", its breadth hardly 0-0008". The other is short and broad ; its length 

 being 0002", and its breadth 0-001". Both have the soft, hazy, indistinct aspect 

 of the larger form, and both, when carefully examined, exhibit the same characters, 

 except that the striation is perhaps somewhat finer. 



(Since the above was written, I have found that this species not only belongs 

 to the complex group, but is one of the most interesting forms in that group. As 

 will be seen in the descriptions of various complex Amphorce, the complex struc- 

 ture is only seen in one focus, while in another, the frustule exhibits the charac- 

 ters of a simple A mphora. This is peculiarly the case in A. spectabilis. The 

 simple view, shown in fig. 80, is so thoroughly simple, that it never occurred to 

 me that it could possibly conceal a second and more complex structure. But 

 when I happened to examine, under a rather high power, and with oblique 

 light, a frustule well placed for bringing out this structure, I detected the appear- 

 ance shown in fig. 80 d. In this case, the coarse transverse striae of the middle 

 part, as seen in fig. 80, were still traceable, at the margin only, on one side, be- 

 cause the frustule did not lie quite fiat. In other examples, no such traces are 

 visible on the complex view, although in general the very strong and elongated 

 central nodules shine through. In fig. 80 d, it will be seen that the whole frus- 

 tule is composed of parallel, longitudinal, very slightly convergent bars, with a 

 narrow sulcus between each two bars. These bars are transversely striated, and 

 the striae, though much finer than even those of the inner and terminal com- 

 partments of the valves, are yet quite distinctly seen, even more so than the 

 others, being apparently free from the haziness above alluded to. Striae of the 

 bars, in this view, about 50 in 0*001". 



In this remarkable form we have the unusual occurrence of three distinct sys- 

 tems of striation ; 1st, The coarse, soft, and hazy transverse striae of the outer and 

 middle compartments of each valve, on the simple view, fig. 80 ; 2dly, On the same 

 view, the finer and radiate striae of the two terminal inner compartments of each 

 valve, which lie in a plane inclined to that of the middle compartments ; and, 3dly, 

 The still finer and parallel striae crossing the longitudinal bands, in the complex 

 view, fig. 80 d, which lie again in a different plane. The frustule is also remarkable 

 for its convexity, which is probably the cause, or one chief cause, of the indis- 

 tinctness of the markings on the simple view.) 



This beautiful species is tolerably frequent in Professor Allman's dredging 

 from Lamlash Bay, and in one from Loch Fine, less so in the other dredgings. 

 The short variety is even more frequent than the typical form. The species 

 has some resemblance to the preceding one in general form and coarseness of 

 striation. But it is at once recognised by its hazy indistinct aspect, by the finer 



VOL. XXI. PART IV. 6 Z 



