KOPOID AND SWEZY: UNAKMORED DINOFLAGELLATA 143 



Amphidinium herdmani nom. sp. nov. 



Text figure U, 2 



Amphidi7iium operculaUim, Herdman (1911a), p. 554; (1911b), pp. 71-75, pi. 8; (1911c), 

 pp. 38-47, figs. 23-26; (1912), pp. 28-36, figs. 8-11; (1913), pp. 19-23, fig. 6. 



Diagnosis. — A small species with broadly ellipsoidal body in ventral view, 

 dorsoventrally compressed, its length 1.16 transdiameters ; girdle anterior; 

 sulcus extending from girdle to antapex; color bright yellow. Length, 50/^. 

 Irish Sea, beach sand at Port Erin, Isle of ]\Ian, April to November. 



Description. — The body is broadly ellipsoidal in ventral view, dorsoventrally flattened, 

 rounded posteriorly and truncate anteriorly, its length 1.16 transdiameters at the widest part. 

 The epicone is a small triangular-shaped portion at the anterior end of the body, W'ith a length 

 on the dorsal side of 0.06, and on the ventral side of the body of 0.36 of the total length of the 

 body, its greatest width being 0.53 transdiameter. The borders of the ventral portion converge 

 posteriorly at an angle of 70°. The apex is truncate. The hypocone is broad ^\-ith rounded sides 

 and a broad, rounded, slightly notched antapex. 



The girdle is placed far anteriorly, its distance from the apex being about 0.06 of the total 

 length on the dorsal side of the body. On the ventral face both ends of the girdle turn posteriorly 

 for a distance of 0.36 of the total length of the body and meet without displacement. The furrow 

 is about 0.06 transdiameter in width, and deeply impressed with overhanging borders. The 

 sulcus extends from the girdle to the antapex, wide at its beginning, contracted below and ex- 

 panding as it nears the antapex, where it sometimes forms a deep notch. The transverse and 

 longitudinal flagella arise near each other at the junction of the girdle and sulcus, probably from 

 the same pore. 



Nucleus and pusules are not figured by Herdman (1911b, c). The central part of the 

 cytoplasm is occupied by a small, spherical body containing a central granule, from which 

 radiate out to the periphery long, slender chromatophores ( ?), bright yellow in color. No striae 

 recorded. 



Dimensions. — Length, 50/^; transdiameter, 43/'. 



Occurrence. — This species has been figured by Herdman (1911, 1912, 1913), 

 from the Irish Sea at Port Erin, Isle of Man, from. April to November. It 

 occurred as greenish brown patches on the sandy beach, a little below high water 

 mark, the largest of which was 50 yards long by 5 yards wide. None was found 

 in the shallow Avaters offshore. These patches were present from a few days 

 to a couple of weeks, when they would disappear to reappear several weeks later. 



Synonymy. — It was described by Herdman (1911) as Amphidimum oper- 

 culatum Clap, and Lach. It differs from that species, however, in its propor- 

 tions, having a broader body, a wide, truncate apex, and a greater length in the 

 epicone : it differs also in its coloring, which is bright yellow. It is therefore 

 proposed as a separate species with the name Amphidinium herdmani nom. 



sp. nov. 



Comparisons. — This species resembles A. tfiiuvatum (fig. U, 3) in its broad, 

 truncate apex, but differs widely from it in all other respects. Its tp^iQ of 

 chromatophores is that of A. opercidatum and A. steini (figs. U, 25, 28). 



