above all, its perfectly transparent, vitreous appearance, were well
described by Dujardin. Stein's _Tropidoscyphus octocostatus_ is a
fresh-water form which may possibly be a distinct species, especially
as it is described with both flagella directed forwards.


[Illustration: Fig. 17.--_Anisonema vitrea_.]


Genus DISTEPHANUS Stöhr.

An aberrant flagellate bearing a single flagellum and a silicious
skeleton resembling those of the Radiolaria. The skeleton consists
of two rings of different diameter parallel with one another and
connected by silicious bars. From the wider ring half a dozen bars
radiate outwards and a similar number of short thorn-like bars point
inwards obliquely. The color is yellow, and except for the flagellum
the form might easily be mistaken for a Radiolarian, as has been the
case repeatedly.


Distephanus speculum Stöhr.

_Dictyocha speculum_ Stöhr; _Dictyocha_ Auc.

With the characters of the genus.

A single specimen only of this very interesting form was seen at
Woods Hole. It occurred in a collection of tow made near the end of
the wharf during the evening.