KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 



421 



NEMATODINIUM gen. uov. 

 Text figures MM, NN 



Diagnosis 



Poiichetiidae with nematocysts ; girdle witli more than 1 turn, displaced 

 more than 0.5 transdiameter ; sulcus with torsion of 0.75 turn or more with a 

 posterior turn on the dorsal side of the antapex ; no ]>aracingular lines ; ocellus 

 distributed or concentrated, located far posteriorly ; eupelagic, marine, holozoic. 

 Type sijecies NemafodijiiKut jxirtitiini sp. nov. 



As yet only three spcies are known in this epi ^i-^^^^^;^^ 



genus, i.e., A^. armatum (= Pouchetia armata suic .J^'/''^'p^^^ "■ 



Dogiel, 1906), from the marine plankton off "«'" "0^^>^^/J 



Naples, Plymouth, and La Jolla, and N. tor- anf.p.---|^--S^^^^----''-- «• 

 pcdo and the type, N. partitnm, fi'om off La ^.^ WV'X^^^^ 



Jolla. This small number of species renders „iv u^sJiAlv^im / "^-Mterca. 



further generic characterization superfluous. '""'^ v7\y^K'\*'' 



^ ^ ^^^ ....V^'S- /. 



Comparisons suic ^'^^■=^^^ '"^'' 



The diagnostic characteristic of this genus „. ,,,, „ ^ ,. . 



'^ '^ Fig. MM. Nematoainmm parUtum sp. 



is the possession of nematocysts clustered uov. Abbreviations: an*, p., antapkal pore; 



a])OUt the nucleus. These are known else- ''P'-' epieone; gir., girdle; hyp., hypoeone; 



, . ,, -r-.. n n J i ■ r, -i i ■ "'■ 9-t ingested Gymnodinium sp. ; interc. a., 



where m the Dmoflagellata only m Pol//l-n- i^tereingular area; l, lens; »,W., melano- 



kos;. These nematocysts are small, sometimes some; n., nucleus; nem., nematocyst; rod., 



slightly capitate, tapering, peg-shaped bodies, '°^2^^' "^%l'^'''"'' "'■ ^'•' t"-^"^^"^-^ '''''• 

 5/^ to 22/^ in length, filled with fluid with an in- 

 trovert consisting of a cone contracting to a straight axial tube extending nearly 

 to the opposite end of the body, where it turns aln-uptly and coils al)out the 

 axial shaft in a close flat spiral. On discharge the tulie is presuma])ly everted 

 as a long coiled thread. The presence of these complex structures affords a 

 sufficient basis for generic distinction. There is no evidence that these organs 

 are inti'oduced from extraneous sources. 



Associated with the pi-esence of these organs is the extreme i^osterior location 

 of the ocellus close to the jiosterior end at the left of the lower j^art of the sulcus. 

 The ocellus is transversely oriented (fig. MM, ].). Of three species known, 

 all have at least 1.5 turns of the girdle and the sulcus exhibits an unusual degree 

 of torsion. In iV. parfifioti there are at least 1.5 turns of this structure, of 

 which only about 0.5 is intercingular, the remainder constituting the anterior 

 and posterior loops, while in N. torpedo there are two turns. This anterior 

 loop may be present in other highlv specialized Pouchetiidae as in PoucJietia 

 vioJaccuw and in several species of Erijthropxis. Rpocialization in their funda- 

 mental structures such as the girdle and sulcus is thus accompanied by special- 

 ization elsewhere in the organism, as in the nematocysts of Ncmafodiiiiiim and 

 tentacle of Erijfhrop.sis, not to mention tlie ocellus of these genera and of 

 Pouchetia. 



