INTRODUCTION. 



In scarcely any department of iiatnral history is the syuonymy so intrieate as in tliat of 

 tlie DiatomaceoB. An enormous number of names has been given to forms, freqnently very ineom- 

 pletely described, or not at all, and often inaccnrately fignred. Moreover tlie literatnre is scattered 

 throngliont papers and periodicals, in many different languages, some of which are of very diiR- 

 cult access. These circumstances, together with tlie necessity of nsing the most excellent and 

 povverfnl lenses, make tlie study of the diatoms a difRciilt one. But that stndy is of considerable 

 importance. These small organisms form a pecnliar dass of liighly developed nnieellular algir, the 

 structural investigation of whicli may bring to light facts of mnch interest. Their silicions shells 

 are very persistent and occnr in a fossil state in strata of clays, marls, limestone etc, belonging 

 to different geological epochs, especially the tertiarj' and post-tertiary, and may becouie of great 

 vallie in geological researches, as certain indications of the nature of the water in which tlie sedi- 

 ments were deposited. When carefnlly stndied the fossil diatoms will surely become as iniportant 

 as the fossil shells. Snch considerations indnced me six years ago to snbject the Diatomacefr to a 

 critical examination, with the principal objects of getting rid of the heavy bnrden of names of slight 

 or obscure import, of limiting as concisely as possible the genera or gronps, speeies and varieties, and 

 of classing them according to tbeir natiiral relations, Every one who knows the amonnt of lite- 

 rature in the diatomology must be aware that snch an enterprise would occupy an ordinary life 

 time, or at any råte a large part of it. It was tlierefore necessary to limit tlie work to some di- 

 vision of the diatoms. The large and beautiful discoid forms bave attracted many workers, and 

 have been described in numerous monographs; but less interest bas been bestowed on the Raphidiese, 

 which are of more importance in the geological researches of my country. I have, then, preferred to 

 limit my present work to the Raphidie;=e which are characterised by the presence of a median line, 

 a feature of their valves which must be of great importance, to jndge from its constant occnrrence 

 in this tribe. 



For the complete knowledge of these diatoms it wonld have been desirable to study them 

 in tbe living state, and complete the splendid work in this direction begun by Pfitzbr; but I bad 

 very little time for snch researches, the examination of many tbousand slides, and drawings of almost 

 all the forms having occnpied me principally, and prevented me from a more extensive study of the 

 living forms, My principal object was to construct a solid basis for farther researches in different 

 directions, and in my opinion the first tliing to be done was to systematize the nomenclature so as 

 to make it possible to recognize tbe forms registered in the science. In the foUowing sjniopsis I 

 have endeavoured to give as exact diagnoses as possible of all forms, belonging to the tribe Ra- 

 phidiece, not omitting any one described or fignred heretofore in a manner to be recognized. I there- 

 fore propose that all names, not mentioned here, may be dropped in oblivion. To give a list of 

 all those names of doubtful or obscure signification wonld be a very fruitless work, but if any of 

 my readers desires to search for snch, be will find them set forth in the catalognes of Habirshaw 

 and of Chase or in the large work recently published by De Toni (Sylloge algaium Vol. II Ba- 

 eillariege Sect. I Raphidiese) in which he has given diagnoses of or at least mentioned all the pu- 

 blished forms. In the last named work also a very valuable list is .supplied of publieations on the 

 diatoms, prepared by Deby, which relieves me from the necessity of giving snch a list here. 



