LEWIS, 0\ DIATOMACE.E. LI.") 



exceeding that of tlie transverse, the interlinear areolae mnst 

 form either squares or |iarallelograms having the longer 

 axis placed in the longitudinal direction of the diatom ; and 

 hence probably the direction of the parallelogram may con- 

 stitute a distinguishing feature in the variety or species. 



I consider the shaded lineation to represent the strife, the 

 interlinear spaces or areolae being of lighter hue. I also 

 resolve unequivocally certain dots in the course of such linea- 

 tion without staying to inquire into their character or nature, 

 as to whether they are elevations or depressions, puncta, 

 papillae, granules, or canaliculi. Nor do I at present enter 

 into an investigation as to their relative coarseness or delicacy 

 of structure, or course of fracture ; nor touch even on the 

 question of focussing. 



It has been stated by some authorities that striae are not 

 to be seen until the diatoms have been boiled in acid ; but 

 this must be an error, as it is common, in most gatherings, 

 to find here and there such a disposition of endochrome as 

 to present no impediment to observation. 



I have recently also found a coarse (42 in •001"), and 

 variable striation upon a slide of Nav, rhomboides, obtained 

 by Mr. Harrison, of Hull, only a few days ago, from a 

 gathering at Thome Moors, near Doncaster; so that thus 

 far our finest reputed striation, especially, is subject to 

 extreme deviation in every instance of careful examination. 



Notes on new and rarer species of Diatom ace m 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 ob- 

 servation during the last three years, together with a list of 

 a few of the more characteristic and generally distributed 

 coast species. 



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 endeavoured, as far as possible, to avoid describing 

 species unless from perfect specimens ; carefully rejecting ail 

 doubtful and imperfect forms. I have also endeavoured to 



