KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 133 



Amphidinium asymmetricum sp. nov. 



Plate 1, figure 1 ; text figure U, 5 



Diagnosis. — Body as\'inmetrically ellipsoidal, longest on its left side, epicone 

 very asymmetrical; girdle a steep spiral, deflected posteriorly at both ends; 

 sulcus confined to the hypocone; chroniatophore yellowish, ramifying; littoral 

 habitat. Length, 48-52*^. Pacific off La Jolla, California, July. 



Desckiption. — The body is asyinmetrieally ellipsoidal, subcircular in cross-section, flattened 

 dorsally, rotund laterally and ventrally, its transverse and dorsoventral diameters about equal 

 throughout tlie middle third of the body. The epieone is very asymmetrical, its length at its left 

 side only 0.1 and at the right ventral region nearly 0.5 of the total length. The apex is asym- 

 metrically rounded iu ventral view and flattened in the dorsal half in lateral view. Its total 

 volume is about 0.2 that of the whole body. The hypocone is sack-shaped, more symmetrical than 

 the epicone, but still .shows some elongation in the left dorsal region homologous with that of 

 the longer left horn of Ccraiium and many other Dinoflagellata. Its greatest length is 1.6 trans- 

 diameters and is found mid-dorsally. The antapex is broadly rounded but longest at the left and 

 dorsad to the main axis. 



The girdle is a rounded trough, ascending about 5 furrow widths from the flagellar pore to 

 the dorsal region, passing horizontally across this and descending thence in a uniform slope of 

 30° on the right face, increasing to 40° on the ventral face in its own distalmost part. Its total 

 displacement between the proximal and distal regions is nearly 0.5 transdiameter. The transverse 

 flagellum completely encircles the body. The length of the sulcus is 0.68 of the total length. It 

 turns to the left anteriorly, and becomes a deep fold in the median plane through the hypocone. 

 It does not extend upon the epicone. Its left border forms a flap which overhangs its right side. 

 The longitudinal flagellum extends posteriorly beyond the antapex for 0.7 of the total length. 

 The posterior flagellar pore is hidden in the deep sulcus. 



The surface is faintly striate with fine parallel lines equidistant on both epicone and h.vpocone, 

 and about ten on the radius. The amyloid body is splieroidal, homogeneous in appearance in 

 life, 0.28 transdiameter in diameter, and centrally located. It is surrounded by a halo of sparsely 

 scattered subspheroidal, highly refractive, oil globules and the whole is enclosed in an unusually 

 large and continuous chromatopliore with blunt, finger-like, peripheral processes which radiate 

 in all directions to the surface. Its color is a uniform pale yellow ochre. The nucleus was not 

 certainly located. It probably lies posterior to the amyloid body as in A. operculatum. 



Dimensions. — Total length, 50/^ transverse diameter at widest point, 30^^; 

 dorsoventral diameter, 28a*; diameter of amyloid body, 7.5/*. 



Occurrence. — Moderately frequent in washings from beach sand on the 

 ocean beach at La Jolla, California, in July, 1914. 



CoisiPARisoNS. — This species is a divergent type of Amphidinium, not far 

 from the G ij rod iuium -like species of Gi/mnodiuium in respect to the large size 

 of tbe epicone. The striatious are similar to those frequently found in G'l/ro- 

 diniuni. It has been placed in Amphidinium because of (1) the asymmetry of 

 the epicone, which is marked and in the same direction as in A. operculatum; 

 (2) the deep ventral sulcus and left flap; and (3) the arrangement of the 

 chromatopliore with respect to the amyloid body. All these features are so 

 consistently indications of Amphidininm that the slightly excessive size of the 

 epicone may be safely disregarded, especially since intermediate stages in size 



