Marine Protozoa from Woods Hole | Page 7

This attractive flagellate was quite common in decaying alg? 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 St?hr.
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 St?hr.
Dictyocha speculum St?hr; 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 Prorocentrid?
2. One or more cross-furrows 3
3. Cross-furrow nearly central Family Peridinid? (cf. Oxytoxum)
Cross-furrow close to Family Dinophysid? anterior end
Several cross-furrows Family Polydinid? and flagella (One genus, Polykrikos.)
KEY TO MARINE GENERA OF PROROCENTRID?.
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 *Exuvi?lla 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 PERIDINID?.
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 DINOPHYSID?.
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 those of the longitudinal furrow usually form great, lateral, wing-like processes ornamented by ribs and other markings.
1. Without shell; longitudinal Genus *Amphidinium furrow may open & close
2. With shell; longitudinal furrow 3 unchangeable
3. With distinct apical funnel 4
No apical funnel Genus Phalacroma
4. With great wing-like ledge 5
Ledges very small; body long, Genus Amphisolenia needle-like
5. Ledge of longitudinal furrow 6 extends to posterior end
Ledge of longitudinal furrow Genus Dinophysis does not extend to posterior end (Recorded by Peck ('93-'95) as very abundant at Woods Hole and in Buzzards Bay.)
6. Ledge is continued dorsally to Genus Ornithocercus the cross-furrow
Ledge is not continued dorsally 7
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 EXUVI?LLA 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.
Exuvi?lla 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