Marine Protozoa from Woods Hole | Page 7

The contractile vacuole is in the anterior neck-like portion
of the body. The flagellum is inserted in a distinct oesophageal tube,
into which the contractile vacuole empties. This tube is continued into a
deeper pharyngeal apparatus of unknown function.
Common in decaying algæ. Length 60µ; greatest diameter 30µ.
[Illustration: Fig. 16.--Two aspects of Astasia contorta.]
Genus ANISONEMA Bütschli
Flagellates with two flagella, of which one is directed forwards and is

concerned with the locomotion of the animal, while the other is
directed backwards and drags after the animal when in motion. Body
slightly compressed dorso-ventrally (fig. 17, section). An oral furrow is
present on the ventral side and the two flagella originate in it (fig. 17, at
left). The vacuole is on the left side. Food vacuoles are present in the
posterior part. The nucleus is central. Movement creeping.
Fresh and salt water.
Anisonema vitrea (Duj.) Fig. 17.
Synonyms: Tropidoscyphus octocostatus Stein '83; Sphenomonas Kent
'81; Ploeotia vitrea Senn 1900.
With the characteristics of the genus. It differs from freshwater forms
in having eight furrowed surfaces running somewhat spirally from the
posterior to the oral end. Length 50µ; width 23µ. This attractive
flagellate was quite common in decaying algæ at Woods Hole; its
shaking movement, its peculiar furrowed surfaces, and, 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.
KEY TO FAMILIES OF DINOFLAGELLIDIA.
1. No crossfurrow; two free flagella Family Prorocentridæ
2. One or more cross-furrows 3
3. Cross-furrow nearly central Family Peridinidæ (cf. Oxytoxum)
Cross-furrow close to Family Dinophysidæ anterior end
Several cross-furrows Family Polydinidæ and flagella (One genus,
Polykrikos.)
KEY TO MARINE GENERA OF PROROCENTRIDÆ.
Diagnostic characters: The transverse furrow is absent and the two
flagella arise from the anterior end of the body. The shell may be
bivalved.
1. No tooth-like process dorsal Genus *Exuviælla to the flagellum
2. With tooth-like process dorsal Genus Prorocentrum to the flagellum
* Presence at Woods Hole indicated by asterisk.
KEY TO MARINE GENERA OF PERIDINIDÆ.
Diagnostic characters: The cross-furrow is nearly central (see, however,
Oxytoxum); the body may or may not have a shell; the shell may or
may not be composed of distinct plates; the plates are distinguished as
equatorial (i.e., bordering the cross-furrow), apical, and antapical,

while still another, the "rhombic plate", may be present, extending from
the cross-furrow to the apex.
1. Without distinct shell Genus *Gymnodinium
With a distinct shell 2
2. Shell not composed of definite 3 plates
Shell composed of definite plates 4
3. Cross-furrow replaced by Genus Ptychodiscus thin-skinned band
Cross-furrow well defined; Genus Protoceratium reticulate markings
raised on shell-surface
Cross-furrow well defined; Genus *Glenodinium no markings
4. Two parts of shell equal or 5 nearly equal
Two parts of shell very unequal 11
5. With transverse flagellum in 6 a distinct furrow
Transverse flagellum not in a 10 furrow
6. With horns, or with wing-like 7 processes
Without processes of any kind 9
7. Processes small, wing-like, Genus Diplopsalis around
flagellum-fissure
Processes horn-like 8
8. Anterior part with 7 equatorial Genus *Peridinium and 1 rhombic
plates
Anterior part with 5 equatorial Genus Gonyaulax and no rhombic plates

Anterior part with 3 equatorial Genus *Ceratium and no rhombic plates
9. Anterior part with 14 equatorial Genus Pyrophacus and 1 rhombic
plates
Anterior part with 7 equatorial Genus Goniodoma plates
Anterior part with 4 equatorial Genus Amphidoma plates
10. Apical extremity drawn out Genus Podolampas into a tube
Apical extremity not drawn out Genus Blepharocysta into a tube
11. Cross-furrow deep, with great Genus Ceratocorys ledge-like walls
Cross-furrow wide, no ledge-like Genus Oxytoxum walls
* Presence at Woods Hole indicated by asterisk.
KEY TO MARINE GENERA OF DINOPHYSIDÆ.
Diagnostic characters: The cross-furrow is above the center of the body,
and its edges, as well as the left edge of the longitudinal furrow, are
usually produced into characteristic ledges; those of the cross-furrow
usually form great funnel-like anterior processes, while