428 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Key to marine genera of Dinophysidse. 
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. 
Without shell; longitudinal furrow may open and close Genus *Amphidinium, p. 432 
With shell; longitudinal furrow unchangeable 3 
With distinct apical funnel 4 
No apical funnel Genus Phalacroma 
With great wing-like ledge 5 
Ledges very small; body long, needle-like Genus Amphisolenia 
Ledge of longitudinal furrow extends to posterior end 6 
Ledge of longitudinal furrow does not extend to posterior end Genus Dinophysis 
(Recorded by Peck (’93-’95). as very abundant at Wood's Hole and in Buzzards Bay.) 
Ledge is continued dorsally to the cross-furrow Genus Ornithocercus 
Ledge is not continued dorsally 7 
With deep dorsal cavity; secondary funnel not notched Genus Citharistes 
No dorsal cavity; secondary funnel deeply notched Genus Histioneis 
Genus EXUVI.2ELLA Cienkowsky ’82. 
(Klebs ’81; Pouchet ’83, ’85.) 
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. 
Exuvisella 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 48/; ; width 44/.; . 
