7. With deep dorsal cavity; Genus _Citharistes_
secondary funnel not notched
No dorsal cavity; secondary Genus _Histioneis_
funnel deeply notched
* Presence at Woods Hole indicated by asterisk.
Genus EXUVIÆLLA Cienkowsky '82.
(Klebs '81; Pouchet '83, '86.)
The form varies from globular to ovoid, with occasionally a sharp
posterior end. Shells are usually somewhat compressed, and consist
of two valves, which frequently slide one over the other in such a
manner as to show the structure with great clearness. The right shell
may have a distinct indentation in the anterior edge. There are two
lateral, discoid, brown chromatophores, each of which possesses a
central amylum granule. The nucleus is posterior. Salt water.
Exuviælla lima Ehr. Fig. 18.
Synonyms _Pyxidicula_ Ehr.; _Cryptomonas_ Ehr.; _Prorocentrum lima_
Kent; _Amphidinium_ Pouchet.
The shell is ovate, rounded and swollen posteriorly. The anterior
border of both shells is slightly indented. The shell is quite thick.
The animal moves through the water very slowly. Dark brown in color.
Length 48µ; width 44µ.
[Illustration: Fig. 18.--_Exuviælla lima_.]
Exuviaella marina Cienkowsky. Fig. 19.
A smaller form than the preceding, more elliptical in outline, with
a thinner shell and with large granules throughout the endoplasm.
The nucleus is spherical and subcentral in position and possesses a
distinct central granule. This may be a small variety of _E. lima_.
[Illustration: Fig. 19.--_Exuviælla marina_.]
Genus GYMNODINIUM Stein '78.
(Bergh '81; Kent '81; Pouchet '83, '85; Entz '84; Schütt '95.)
The general structure of these forms is similar to that of
_Glenodinium_; the most striking and positive difference is the
absence of a shell. The animals are, as a rule, spherical, yet they
may be pointed at the two ends or at one of them. They are also
frequently flattened dorso-ventrally. The transverse furrow may
be either circular and straight around the body or may describe a
spiral course, passing even twice around the body. The flagella
arise near cross-furrow or, in some cases, in longitudinal furrow.
Chromatophores may or may not be present and food-taking is holozoic,
in many cases at least. In some cases ectoplasm and endoplasm can be
distinguished. Fresh and salt water.
Gymnodinium gracile Bergh '82, var. sphærica, n. Fig. 20.
The body is divided by the transverse furrow into a shorter anterior
and a longer posterior part. The longitudinal furrow is broader at
the posterior extremity than at the cross-furrow. The structural
feature upon which this new variety is made is the unvarying
plumpness of the body, making it almost spherical, except for
a slight flattening dorso-ventrally. The nucleus is large and
ellipsoidal, with characteristic longitudinal markings of chromatin.
The endoplasm is evenly granular, with a number of large ingested
food bodies. The color is brown, not rose-red as in Bergh's species,
nor is the Woods Hole form as large as the latter. Length of body
68µ; width 55µ. Common.
[Illustration: Fig. 20.--_Gymnodinium gracile_, var. _sphærica_.]
Genus GLENODINIUM (Ehr.), Stein '83.
(Bergh '82; Bütschli '86; Pouchet '85; Daday '86.)
Small globular forms with two distinct furrows, one transverse around
the body, the other longitudinal upon the face only. The shell is
soft and structureless with a distinct aperture near the meeting
point of the two furrows. The endoplasm usually, but not always,
contains a bright red eye-spot.
Fresh and salt water.
Glenodinium compressa, n. sp. Fig. 21, a, b, c.
This species resembles _G. acuminata_ of Ehrenberg except that it is
strongly compressed laterally. The longitudinal furrow extends nearly
to the extremity of the animal. It begins as a narrow slit and widens
as it progresses upon the left side; it also becomes much deeper
on this side and at the bottom of the depression the longitudinal
flagellum is inserted. The transverse furrow runs evenly around the
body near the upper pole, giving to the shell almost the aspect of
an _Amphidinium_. Brown chromatophores may or may not be arranged
radially about a central amylum granule. One striking characteristic
is the depth of the two furrows. The nucleus is elongate and somewhat
curved; it lies against the posterior wall of the rather thick shell.
Not uncommon.
Length 40µ; breadth 32µ; width 18µ.
The posterior end of the animal is often somewhat pointed and this
point frequently becomes attached, so that the animal whirls around
upon it as upon a pivot.
[Illustration: Fig. 21 a, b, c.--_Glenodinium compressa_, n. sp.]
Glenodinium cinctum Ehr. Fig. 22.
The body is globular, smooth, and homogeneous. Brown chromatophores
arranged radially, each in the form of a cone, the base of which
rests against the shell while the points turn inward. A bright-red
eye-spot may or may not be present; when present it is placed near
the junction of the two furrows. The longitudinal furrow is small.
Fresh water and salt.
Length and diameter the same, 21µ.
This species was observed by Peck '93.
[Illustration: Fig. 22.--_Glenodinium cinctum_.]
Genus PERIDINIUM Ehr. '32, Stein '83.
(Claparède & Lachmann '58; Bergh '81; Pouchet '83; '85; Gourret '88;
Bütschli '86.)
The form is globular, ovoid or elongate, the apex frequently drawn
out into a long tube. The transverse and longitudinal furrows are
quite distinct, the former having often a spiral course about the
body. The two halves of the body are similar, the posterior being
somewhat shorter; the anterior half has seven equatorial plates, an
oral plate, two lateral apical plates, and one or two dorsal plates.
The two antapical plates frequently have a tooth-like process. The
bodies are colorless, green or brown.
Fresh and salt water.
Peridinium digitale Pouchet. Fig. 23.
Synonyms: _Protoperidinium digitale_ Pouchet; _Protoperidinium_ Bergh
p. p.; _P. divergens_ Peck.
The shell is covered with pits of large size. The posterior part
is hemispherical and surmounted by a single horn or spine. The
transverse furrow is very oblique, and its two extremities are united
by a sigmoid longitudinal furrow. The anterior half bears two spines
or horns of different size, and variable. The nucleus is spherical
or ellipsoidal and placed in the posterior half of the shell.
Length 68µ; diameter 54µ. Common.
Although the description of Pouchet's _P. digitale_ differs in some
respects from a careful description of the Woods Hole form, I think
the species are the same. The chief difference is in the single horn
of the posterior half; in Pouchet's form this is furrowed by a narrow
groove which runs to the S-shaped longitudinal furrow. In the Woods
Hole form I was unable to make out such a furrow. The flagella, also,
were not seen. This same form was pictured by Peck '95 as _P.
divergens_.
[Illustration: Fig. 23.--_Peridinium digitale_.]
Peridinium divergens Ehr. Fig. 24.
Synonym: _Ceratium divergens_ Kent.
The shell is spheroidal, widest centrally, attenuate and pointed
posteriorly; the anterior portion is armed with two short, pointed
horns, each of them having a toothed process at the basal portion
of the inner margin. They are frequently colorless and beautifully
transparent, the body being free from large opaque granules; again
they are colored brown or yellow. The nucleus is large and elongate
and finely granular. 75µ long and 68µ in diameter. Common.
[Illustration: Fig. 24.--Ventral and dorsal aspects of _Peridinium
divergens_.]
Genus CERATIUM (Schrank).
(Stein '78; Perty '52; Clap & Lach. '58; Bergh '82; Pouchet '83;
Gourret & Roeser '88; Bütschli '85; Kent '81; Senn 1900; Schütt '98.)
The general shape is a flattened sphere with three long processes
or horns. The cross-furrow is either spiral or circular; the
longitudinal furrow is usually wide and occupies the greater part of
the anterior half of the shell. The shell is thick, reticulate or
striped, and sometimes provided with short spines; often distinctly
porous. The anterior half is composed of 3 equatorial and 3 apical
plates, the latter being continued into the horn-like process. The
posterior half is composed of 3 equatorial and one apical plate
continued into the posterior horn. The right posterior plate is
continued into a similar horn which may remain rudimentary or be
continued into a considerable process. Similarly the left posterior
horn is usually developed, but remains small. There may be from 2 to
3, 4, and 5 horns. Chromatophores usually present, green to yellow
brown.
Fresh and salt water.
Ceratium tripos Ehr. Fig. 25.
The body is somewhat triangular and bears three horns, two of which
are shorter than the other one and slightly curved upward.
Length, including the horns, 290µ.
[Illustration: Fig. 25.--_Ceratium tripos_.]
Ceratium fusus Ehr. Fig. 26.
Synonym: _Peridinium fusus_ Ehr.
The animal is very elongate, due to the presence of two long horns
at the extremities of the body. Color, yellow with chromatophores.
Length 285µ; width 23µ.
Both of these species are common in the tow and in the algæ at the
edge of the wharf. Both of them are mentioned by Peck in '93 and '95.
[Illustration: Fig. 26.--_Ceratium fusus_.]
Genus AMPHIDINIUM Clap. & Lach.
The body is ovoid to globular and usually much flattened
dorso-ventrally. The anterior portion is very much reduced and is
somewhat head-like or cap-like. The longitudinal furrow extends
through the entire posterior body length and is apparently capable
of widening and narrowing. It is probably naked (see here Klebs,
Pouchet, Bütschli), although Stein maintained that there is a
delicate cuticle-like shell. Chromatophores of brown or green colors
present and usually grouped radially about a central amylum granule.
The nucleus is posterior.
Fresh and salt water.
Amphidinium operculatum Clap. & Lach. Fig. 27.
The body is oval and flattened. The transverse furrow is at the
extremity (posterior) of the body and the small portion, which is
thus apparently cut off, is the cap-like or operculum-like structure
which gives the name to the species. Klebs maintains that the two
furrows are not connected, but in this he is certainly mistaken,
provided we have the same species under consideration. Very common
about Woods Hole.
Length from 40 to 50µ; width 30µ; thickness 15µ.
[Illustration: Fig. 27.--_Amphidinium operculatum_.]