72 Transactions of the Boy al Microscopical Society. 
by the author of the ‘ Synopsis.’ * The ordinary arrangement thus 
coinciding with the natural system. — F. K.] 
12th Tribe, Licmophore.® (Fig. 13). 
The endochrome in this tribe preserves the same disposition as 
in the two preceding; but the frustules are cuneiform as in the 
Meridiem, presenting this peculiarity that between the two primary 
are developed a certain number of supernumerary valves to which 
we have given the name of diaphragms. This modification in the 
physical structure of the frustule leads to the tribe of the Tabellariem, 
in which we meet with the genera containing an illimitable number 
of diaphragms : ex., Striatella. 
1st section, diaphragm rudimentary. Podosphenia, Licmo - 
phora. 
2nd section, two diaphragms. Climacosphenia. 
[The portions of the frustule here called diaphragms are the 
annuli and septae of the ‘ Synopsis.’ | The late Professor W. Arnott 
once suggested to me that these annuli were perhaps abortive 
valves. In this view I cannot concur. — F. K.J 
13th Tribe, Tabellaki£es (Fig. 24). 
This tribe is composed of all the classes of Diatomacem of 
which the frustules are not cuneiform, and are furnished with 
internal diaphragms. The granular endochrome, which is scattered 
in most of the genera, here unites in the form of a star very similar 
to the genus Striatella, and forms thus the passage from the 
Tabellarieee to the Biddulpliiese. 
1st section, Frustules furnished with two diaphragms. Dia- 
tomella, Grammatophora. 
2nd section, Frustules furnished with more than two dia- 
phragms. 
^Granular endochrome disposed without order. Tabellaria, 
Tetracyclus, Bliahdonema. 
**Granular endochrome radiating from a central point. Stria- 
tella (Fig. 15). 
14th Tribe, Biddulphieje. 
I unite in this tribe the Anguliferae and the Biddulphieae of 
authors, seeing that they have a common characteristic, the 
granular endochrome disposed in lines radiating from a central 
point. The development of the frustules is also the same in every 
species of these two groups, which thus form one very natural 
tribe. In most of the species the frustules are furnished with 
appendices ; as to their form, it is most variable. Sometimes the 
frustules are very irregular, sometimes they affect a geometrical 
* ‘ Synopsis,’ vol. ii. p. 16. t Yol. ii. p. 32. 
