Part 7 (1/2)

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 EXUVIaeLLA Cienkowsky '82.

(Klebs '81; Pouchet '83, '86.)

The form varies from globular to ovoid, with occasionally a sharp posterior end. Sh.e.l.ls 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 sh.e.l.l may have a distinct indentation in the anterior edge. There are two lateral, discoid, brown chromatoph.o.r.es, each of which possesses a central amylum granule. The nucleus is posterior. Salt water.

Exuviaella lima Ehr. Fig. 18.

Synonyms _Pyxidicula_ Ehr.; _Cryptomonas_ Ehr.; _Prorocentrum lima_ Kent; _Amphidinium_ Pouchet.

The sh.e.l.l is ovate, rounded and swollen posteriorly. The anterior border of both sh.e.l.ls is slightly indented. The sh.e.l.l is quite thick.

The animal moves through the water very slowly. Dark brown in color.

Length 48; width 44.

[Ill.u.s.tration: Fig. 18.--_Exuviaella lima_.]

Exuviaella marina Cienkowsky. Fig. 19.

A smaller form than the preceding, more elliptical in outline, with a thinner sh.e.l.l 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_.

[Ill.u.s.tration: Fig. 19.--_Exuviaella marina_.]

Genus GYMNODINIUM Stein '78.

(Bergh '81; Kent '81; Pouchet '83, '85; Entz '84; Schutt '95.)

The general structure of these forms is similar to that of _Glenodinium_; the most striking and positive difference is the absence of a sh.e.l.l. 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, pa.s.sing even twice around the body. The flagella arise near cross-furrow or, in some cases, in longitudinal furrow.

Chromatoph.o.r.es 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. sphaerica, n. Fig. 20.