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IX. ^ew Peridiniacese from the Atlantic. By George Muriiay, F.R.S., F.L.S., 

 Keeper of Botany, British Museum, and Erances G. Vi^wittiisQ, former Student 

 of Newnham College, Cambridge, 



(Plates XXA^II.-XXXIII.) 



Read 1 9th January, 1890. 



JLHE material described in the following paper \vas collected by Messrs. Murray and 

 Blackman, during a voyage made in U.M.S. 'Para' (June, July, and August 1897), 

 while engaged in a study of the Coccospheres and llhabdosplieres, and other forms of 

 Phyto-plankton described elsewhere. Previous to this voyage in the ' Para,' and 

 subsequently in the ' Medway ' and ' Atrato,' Captain W. llaultain Milner (by the 

 pumping method, employed in all cases cited here) has collected with the greatest 

 success, while other collections have l)een contributed by Capt. Uudge on the * Avon,' 

 Capt. Tindall on the ' Elbe,' and Capt. Alex. Turbyne, while a passenger to the Cape 

 on the ' Dunvegan Castle.' 



Almost the whole of our previous systematic knowledge of the marine Peridiniacese is 

 derived from Stein's ' Infusionsthiere ' and Schiitt's ' Peridiniaceae ' in the ' Ergebnisse 

 der Plankton Expedition der Humboldt-Stiftung,' these writers having included in their 

 treatment observations of older workers such as Ehrenberg. Stein, however, gives no 

 formal diagnoses of genera and species, though his excellent figures clearly indicate 

 the characters of his forms. Schiitt also reserves such diagnoses for a future volume, 

 contenting himself with a morphological exposition of the group, and with figures of his 

 new and other species in the book cited and in his ' Pflanzenleben der Hochsee.' He 

 has supplemented his text and figures, however, by giving the characters of the genera 

 in his ' Peridiniales,' in Engler and Prantl's * Natiirlichen Pflanzenfamilien.' Even then, 

 we have been compelled to represent here a few of his species for greater accuracy 

 in certain details. 



As yet no one has shown an examj^le of the description of specific characters. In 

 writing these for the present memoir we have found many difficulties, and the chief 

 of these, in spite of Schiitt's work, was the determination of what should be generic 

 and what specific characters. In consideration of the fact that we are as yet merely at 

 the beginning of the systematic study of marine Peridiniacese, and that the exploration 

 of great tracts of ocean has yet to be undertaken with doubtless many new forms to be 

 revealed, we have decided that it would lead to less eventual confusion if we included 

 characters that at present look Hke generic characters among the specific. We have 

 done so deliberately in a few cases, having been warned by our experience in the 

 modification of the generic character by the addition of the new species we here describe. 

 It is clear that there are already, too many genera, and farther exploration may be 



SECOND SERIES. — BOTANY, VOL. V. 3 B 



