NEW FORMS OF MARINE DIATOMACEZ. 519 
sidered as only a single frustule, while the Cymbella or Cocconema would be called 
a double one. 
I confess I feel disposed to consider both in the same light, as double forms. 
If that be correct, then what is usually called the valve of an Amphora will be 
an entire frustule, and what is usually called the entire frustule (as in figs. 63 to 
72, for example) will be considered as two frustules in the act of self-division, but 
still united by the connecting membrane. 
One reason why I incline to this view is, that what, on this principle, are to 
be called single frustules, which are now regarded as halves or single valves, are 
often much more frequent than the entire, or, as I should say, double frustules. 
We never see the halves of Navicule separated in this way. Secondly, Each single 
valve, or as I should say frustule, has three nodules; but the entire or double 
frustules have six. Thirdly, In Amphore, the two halves of the double or entire 
frustule are almost always separated by a rectangular space, apparently homo- 
logous with the connecting membrane, which is seen in other genera when in a 
state of self-division. When this is absent, as in fig. 81 ¢, or in fig. 76, the form 
has exactly the appearance of a twin frustule of Cymbella. Lastly, If we regard 
the so-called valves as entire frustules, they become perfectly analogous, in gene- 
ral form and structure, to Cymbellze or Cocconemata; and we shall find, in the 
remarkable group of Complex Amphoree, next to be described, that the segments 
in many species, indeed in most, have a still greater resemblance to Cymbelle or 
Cocconemata. 
Let us now consider that group. 
B. Complea Amphore. 
Of this sub-group, as I have already stated, there are, in these materials, as many 
as of the simple group just described. These species are as follows :— 
82. HOPS lyrata, n. sp. 92. goRPhem sulcata, Breb. 
83. Milesiana, n. sp. 93. acuta, n. sp. 
84. ... elongata, n. sp. 94. ...  erassa, Greg. 
85. --.  quadrata, n. sp. | 95. ... pusilla, n. sp. 
86. ...  excisa, n. sp. 96. ...  granulata, n. sp. 
87. ... nobilis, n. sp., G. 97. ...  eymbifera, n. sp. 
88. -» Arcus, Greg. 98. +. proboscidea, n. sp. 
89. ...  Grevilliana, Greg. 99. ...  costata, Sm. 
90. ...  complexa, n. sp. | 100. ... _ bacillaris, n. sp. 
91. ...  fasciata, n. sp. 
The first species of this group which was figured was A. costata, Sm. But the 
remarkable peculiarity of its structure was not specially noticed. I subsequently 
noticed several species in the Glenshira Sand, in which the complex structure had 
attracted my attention, such as A. Arcus, A. Grevilliana, and A. crassa, which 
I described and figured. I also pointed out that the same structure occurs in 
A. costata, Sm. In the new materials, besides acquiring a more accurate know- 
ledge of the three new species just named, all of which I here figure a second 
