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 (cf. Oxytoxum) | Family [Peridinidæ] |
| Cross-furrow close to anterior end | Family [Dinophysidæ] | |
| Several cross-furrows and flagella | Family Polydinidæ (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 to the flagellum | Genus *[Exuviælla] |
| 2. | With tooth-like process dorsal to the flagellum | Genus Prorocentrum |
| * 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 plates | 3 |
| Shell composed of definite plates | 4. | |
| 3. | Cross-furrow replaced by thin-skinned band | Genus Ptychodiscus |
| Cross-furrow well defined; reticulate markings raised on shell-surface | Genus Protoceratium | |
| Cross-furrow well defined; no markings | Genus *[Glenodinium] | |
| 4. | Two parts of shell equal or nearly equal | 5 |
| Two parts of shell very unequal | 11 | |
| 5. | With transverse flagellum in a distinct furrow | 6 |
| Transverse flagellum not in a furrow | 10 | |
| 6. | With horns, or with wing-like processes | 7 |
| Without processes of any kind kind | 9 | |
| 7. | Processes small, wing-like, around flagellum-fissure | Genus Diplopsalis |
| Processes horn-like | 8 | |
| 8. | Anterior part with 7 equatorial and 1 rhombic plates | Genus *[Peridinium] |
| Anterior part with 5 equatorial and no rhombic plates | Genus Gonyaulax | |
| Anterior part with 3 equatorial and no rhombic plates | Genus *[Ceratium] | |
| 9. | Anterior part with 14 equatorial and 1 rhombic plates | Genus Pyrophacus |
| Anterior part with 7 equatorial plates | Genus Goniodoma | |
| Anterior part with 4 equatorial plates | Genus Amphidoma | |
| 10. | Apical extremity drawn out into a tube | Genus Podolampas |
| pical extremity not drawn out into a tube | Genus Blepharocysta | |
| 11. | Cross-furrow deep, with great ledge-like walls | Genus Ceratocorys |
| Cross-furrow wide, no ledge-like walls | Genus Oxytoxum | |
| * 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 those of the longitudinal furrow usually form great, lateral, wing-like processes ornamented by ribs and other markings. | ||
| 1. | Without shell; longitudinal furrow may open & close | Genus *[Amphidinium] |
| 2. | With shell; longitudinal furrow unchangeable | 3 |
| 3. | With distinct apical funnel | 4 |
| No apical funnel | Genus Phalacroma | |
| 4. | With great wing-like ledge | 5 |
| Ledges very small; body long, needle-like | Genus Amphisolenia | |
| 5. | Ledge of longitudinal furrow extends to posterior end | 6 |
| Ledge of longitudinal furrow does not extend to posterior end (Recorded by Peck ('93-'95) as very abundant at Woods Hole and in Buzzards Bay.) | Genus Dinophysis | |
| 6. | Ledge is continued dorsally to the cross-furrow | Genus Ornithocercus |
| Ledge is not continued dorsally | 7 | |
| 7. | With deep dorsal cavity; secondary funnel not notched | Genus Citharistes |
| No dorsal cavity; secondary funnel deeply notched | Genus Histioneis | |
| * Presence at Woods Hole indicated by asterisk. | ||