72 PEOF. W. A. HERDMAN ON THE OCCURRENCE OF 



only ; and A. operculatum, which is stated to occur in brackish water on the 

 north coasts o£ Europe. In addition, Kofoid (' Dinoflagellata of the San 

 Dieo-o Keoion,' 1907), records A. lacustre from fresh water, A. aculeatiim, a 

 pelagic form from Naples, and A. sulcatum, which he took in a vertical haul 

 from 90 fathoms in the Pacific. 



On huntino- through the few scattered references to A. operculatum which 

 occur, one finds, however, that R. S. Bergh, in the ' Zoologischer Anzeiger" 

 for 1882, states (p. 693) that Spengel in December and January found it in 

 huo-e quantities on the beach at Norderney. Although, therefore, Amphi- 

 dinium' operculatum. has been recorded once before as occurring in quantity, 

 the occurrence appears to be a sufficiently rare event to be worthy of notice ; 

 and, so far as I can ascertain, the species, although known from several parts 

 of North-west Europe, has not been previously found on the British coasts. 

 I have written to most of the marine laboratories (Plymouth, Cullercoats, 

 St. Andrews, and Millport) and to many marine biologists and have not been 

 able to hear of any British record. 



It is, however, not an unknown thing for rare Dinoflagellates to appear 

 suddenly in some locality on an occasion in phenomenal quantities. Torrey, 

 in the ' American Naturalist ' for 1902, describes the unusual occurrence of 

 a species of Gonyaulax on the coast of California. Sherwood and Vinal 

 Edwards, in the ' Bulletin of the United States Bureau of Fisheries ' for 

 1901, tell how for two weeks in September a Pmc^mmw infested Narragansett 

 Bay in such numbers as to colour the water blood-red and cause the death 

 of many fishes. 



Finally, Whitelegge, in the ' Records of the Australian Museum ' for 1891, 

 o-ives an interesting account of a new species of Glenodiniinn [G. rubrum) 

 which appeared in such quantities in Port Jackson as to give the water " the 

 appearance of blood'' and cause the death of great numbers of oysters, 

 mussels, and all forms of shore life. Whitelegge supposed that the very 

 heavy rainfall that year, by affecting the salinity of the water, and then a 

 lengthened period of calm weather which followed, may have provided 

 favourable conditions for an unusual development of the Dinoflagellata. 

 The Glenodinimn appeared in vast numbers about the middle of March and 

 disappeared early in May. When it was at its climax, the allied colourless 

 species Gymnodinium spirale appeared in the bay and soon increased greatly in 

 numbers and became finally even more abundant than the red Glenodinium 

 upon which it was evidently feeding. 



Returning now to our AmpJddinium op>ercidatum, it is not easy to account 

 for the sudden appearance of this unusual Dinoflagellate (previously un- 

 recorded in Britain) in such profusion on the beach at Port Erin last April. 

 Plankton hauls were being taken regularly across the bay at the time, and 

 they showed no trace of the organism. In fact, Amp/tidinium has not 

 occurred in any of the thousands of gatherings which we have taken in the 



