63 



THE NEW CONSPECTUS OF THE FAMILIES AND 

 GENERA OF DlATOMACEiE. By Professor H. L. Smith, 

 of Geneva College, New York. 



The July part of the " Lens" contains the Index to the above 

 Conspectus. It will be found that the Professor has applied the 

 pruning knife most unsparingly, doubtless to the great disgust of 

 the " species mongers." Some of the genera might, Ave think, 

 have been retained with advantage ; for example, the Campylo- 

 disci, which has been relegated to the Surirellai. This genus has 

 two unvarying characteristics, viz., the circular form of the valves, 

 and the median space of the two valves of the frustule are always 

 at right angles to each other; consequently the valve must be 

 truly circular. Professor W. Smith, the author of the Synopsis, 

 has erred in placing Campylo discus spiralis in that genus. Kut- 

 zing was right in making it a species of Surirella (S. spiralis). 



The union of the genera Triceratium and Amphitetras with Bid- 

 dulphia we think will not be generally accepted ; to do so necessitates 

 the enlargement of the generic characters of the last to too great 

 an extent. The number of species will also be inconveniently 

 large.* 



The genus Triceratium might, we think, be united to Amphite- 

 tras without much alteration of the generic character. The author 

 is, no doubt, right in abolishing the conditions of stipitate, tubular, 

 &c, as being of no value. He remarks, " The conditions frondose, 

 stipitate, filamentous, tubular, &c. I have not considered sufficient to 

 warrant the formation of new genera. A long study of living 

 forms has convinced me that these characters are fleeting — not to 

 be relied on. 



" Among the Schizonemea?, e. g., the fronds are quite variable 

 which enclose the same siliceous frustules ; and the fronds them- 

 selves vary with the habitat. The tubes of Colletonema and En- 

 cyonema disappear in quiet waters, and the frustules become 

 embedded in amorphous jelly, or quite free." 



The number of genera dealt with in the Conspectus, and which 

 the Professor says "includes, as far as I am aware, either as ad- 

 missible or among the synonyms, the name of every genus hitherto 

 constituted," is 299; the number deleted is 189, thus abolishing 

 nearly two-thirds ! ! ! 



We find on comparing the Conspectus with the Synopsis of British 

 Diatoinaceae 23 out of the 59 genera described therein deleted. 



The following list shews the genera retained, but in order to 



* The author will no doubt complete the Synopsis by publishing a Conspectus 

 of the Species of Diatomaceas. 



