MARINE PROTOZOA FROM WOODS HOLE. 
427 
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. 
Genus DISTEPHANIJS Stohr. 
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 liars 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 Stohr. 
Dictyocha speculum Stohr; 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 Dinqflagellidia. 
1. No cross-furrow; two free flagella .4 Family Prorocentridx 
2. One or more cross-furrows 3 
3. Cross-furrow nearly central (cf. Oxytnxum) Family Peridinidse 
Cross-furrow close to anterior end Family Dinophysidse 
Several cross-furrows and flagella Family Polydmidse 
(One genus, Polykrikos.) 
Key to marine genera of Prorocentridse. 
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 * Exuvisella, p. 428 
2. With tooth-like process dorsal to the flagellum Genus Prorocentrum 
Key to marine genera of Peridinidse. 
Diagnostic characters: The cross-furrow is nearly central (see, however, Oxytoxu.m)\ 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 antapieal, while still another, the “rhombic plate,” may be present, extending from the 
cross-furrow to the apex. 
1 . 
2 . 
3. 
4. 
5. 
6. 
7. 
9 . 
10 . 
11 . 
Without distinct shell 
With a distinct shell 
Shell not composed of definite plates 
Shell composed of definite plates 
Cross-furrow replaced by thin-skinned band 
Cross- furrow well defined; reticulate markings raised on shell-surface 
Cross-furrow well defined; no markings 
Two parts of shell equal or nearly equal 
Two parts of shell very unequal 
With transverse flagellum in a distinct furrow 
Transverse flagellum not in a furrow 
With horns, or with wing-like processes 
Without processes of any kind 
Processes small, wing-like, around flagellum-fissure 
Processes horn-like 
Anterior part with 7 equatorial and 1 rhombic plates 
Anterior part with 5 equatorial and no rhombic plates 
Anterior part with 3 equatorial and no rhombic plates 
Anterior part with 14 equatorial and 1 rhombic plates 
Anterior part with 7 equatorial plates 
Anterior part with 4 equatorial plates 
Apical extremity drawn out into a tube 
Apical extremity not drawn out into a tube 
Cross-furrow deep, with great ledge-like walls 
Cross-furroW wide, no ledge-like walls 
Genus * Gymnodinium, p. 429 
3 
4 
Genus Ptychodiscus 
Genus Protoceratium 
Genus * Glenodinium, p. 429 
5 
11 
. 6 
- 10 
7 
9 
Genus Diplopsalis 
8 
. .Genus * Peridinium, p. 430 
Genus Gonyaulax 
Genus * Ceratium, p. 431 
Genus Pyrophacus 
Genus Goniodoma 
Genus Amphidoma 
, Genus Podolampas 
Genus Blepharocysta 
Genus Ceratocorys 
Genus Oxytoxum 
