1871.] . 257 [Edwards. 



This form, as its general contour and characters plainly indicate, 

 belongs, as I have said, to the genus Gyrosigma, which Hassall 

 founded for the reception of the sigmoid forms hitherto included in 

 Ehrenberg's genus Navicula, from which he thus very properly, as 

 has been since proved, separated them. Subsequently to HassalPs 

 division of the genus in this manner, W. Smith bestowed the name 

 Pleurosigma upon the same group, and this last designation is the one 

 most commonly in use at the present time to distinguish this genus. 



I must here be permitted to make a few remarks in connection 

 with the subject of nomenclature, as at the present time in use by 

 writers when treating of this family of vegetable organisms. It does 

 not appear to be generally known to such persons that certain rules 

 of nomenclature, to be used when describing or speaking of natural 

 objects, and more especially animals and plants, have been devised, 

 and from their plainly apparent rationality and admirable applica- 

 bility, adopted very generally by biologists in all countries. It 

 would be extremely advisable, therefore, for all students of the 

 Diatomacese, before venturing into print, to make themselves 

 thoroughly acquainted with these rules, and to frame their publica- 

 tions thereon. One of these rules strongly deprecates the giving of 

 new names to groups of natural objects, as plants or animals, which 

 have already had designations applied to them, accompanied by suffi- 

 ciently distinctive descriptions to admit of their recognition at any 

 future time, at the fancy of any new observer, or for other insuffi- 

 cient reasons. The rule itself is briefly stated thus: "Karnes given to 

 species or groups unaccompanied by published characteristic descrip- 

 tions, should yield place to the earliest name accompanying such 

 descriptions." 



To prevent mistakes occurring in biological nomenclature, of course 

 great care is required, and considerable research necessary. In fact, 

 it can hardly be denied that it would be much better if, as a general 

 rule, students, before bestowing a name on a form new to them and 

 apparently separable on good grounds from some already established 

 group, would even rather tend to err upon the one side than the 

 other; that is to say, permit the retention of a name already pub- 

 lished, but unaccompanied by a sufficiently distinctive description, if 

 they can nevertheless satisfy themselves that the form they have 

 under examination is without doubt that previously named. Such a 

 conclusion can, of course, most surely be arrived at by the examina- 

 tion of authentic specimens, but sometimes, also, although not in so 



PROCEEDINGS B. S. N. H. — VOL. XIV. APRIL, 1872. 



