NATURAL SCIENCES OF PHILADELPHIA. 61 



Notes on new and rarer species of Diatomaceae of the United States Sea 



Board. 



BY F. W. LEWIS, M. D. 



The present communication contains brief notices of some of the rarer and 

 hitherto undescribed species of Diatomacese of the United States Sea Board, 

 which have fallen under my observation during the last three years, together 

 with a list of a few of the more characteristic and generally distributed coastal 

 sjiecies. 



The forms to be described are mostly salt-water or brackish. A few species, 

 however, known as fresh-water will be noticed where these have been found 

 domesticated along with the marine. 



I have endeavored, as far as possible, to avoid describing species unless from 

 perfect specimens ; carefully rejecting all doubtful and imperfect forms. 

 Sources of error arising from the great variation in size, outline, and striation, 

 and from the absence of certain and positive indications whereby ihe sporan- 

 gial may be detected and classified with its typical variety, I have also en- 

 deavored to guard against. The want, however, of several important consult- 

 ing authorities on this branch in the Academy's Library, together with the 

 not always satisfactory character of the material furnishing the data of this 

 paper, often consisting of muds and mixed gatherings, must be my excuse for 

 any errors or inadvertencies which may be found in its pages. 



Among those to be described will be introduced one or two doubtful forms, 

 probably sporangial, as Amphiprora pulchra Bailey, and extraordinary 

 varieties of Surirella ovata and Triceratium a 1 1 e r n a n s, both of which last 

 are figured. 



It is proposed to consider the species to be noticed in the following order : 

 1. " New species and sporangial forms." 2. " Rare species and species not 

 hitherto noted as belonging to this country.'''' 3. " Species characteristic of the 

 American coast." 4. " Species of universal distribution." 



The precise locality and nature of the gathering from which specimens have 

 been derived will be indicated, excepting where species are of general distribu- 

 tion and very abundant along the coast, along with such other distinctive 

 characters as may be necessary for the definition of new or doubtful species ; 

 and as it is not intended that the summary shall present a complete resume 

 of native marine species, mention of many forms known to me not referable 

 to one or other of the above four divisions will be omitted. 



It may not here be out of place to add, that the result of my limited investi- 

 gations convinces me that a rich and unexplored field lies open in the United 

 States for those whose time and attention may hereafter be directed to this 

 branch of microscopic research, a branch, until very recently, comparatively 

 neglected in this country. Perhaps a reason for this neglect may be found in 

 the great interest attaching to the less laborious study of the numerous fossil 

 diatomaceous deposits of our country, and of the new and ever varying guanos 

 so frequently finding their way to our shores. Without any intention of un- 

 dervaluing the importance of researches on fossil botany, it may yet be doubted 

 whether results so satisfactory and important to science are likely to accrue, 

 as when the living forms are the subject of study. Nothing certainly would 

 seem so well calculated to dampen the ardor of physiological inquiry as pro- 

 longed and laborious examinations of the minute detail of the silicious skele- 

 tons of these organisms without reference had to the kind and manner of life 

 they once invested. 



As an additional argument in favor of the study of living species it may here 

 be mentioned that many of the fossil forms are still to be found as living spe- 

 cies on the coast, or under circumstances which prove them to have been alive 

 at no very remote period. It is not unusual to meet with some of these in 

 the Delaware tidal mud, and a still larger number are to be found in the blue 



1861.] 



