ATLAS DER DIATOMACE^-KUNDE. 135 



to 660 diameters (excepting, of course, wliere the original is less 

 than 900 diameters). Photography has been employed for the 

 purpose of this reduction, and the negatives printed by the 

 autotype process (Lichtdruck). The plates have thus all the per- 

 manence of those produced by lithography or engraving, and also 

 the advantage of every figure being an exact fac simile of the 

 author's drawings. The absence of correctness in copying has 

 frequently been complained of by Greville, Donkin, and others. 



The first part contains four plates (16 X 11). The first plate 

 contains 26 figures of Actinoptychi, six of which are devoted to 

 A. undulatus, the others to those forms known as Heliopelta and 

 Omphalopelta, two species of Triceratium, viz , T. JSfarylandicum, 

 Brightwell, and T.Amblyoceros, Ehrenberg, and placed in this genus. 

 The correctness of this is, perhaps, open to question. The beauty 

 and accuracy of these figures will strike every observer who is 

 acquainted with these remarkable forms. 



Plate II. contains 37 figures of the lyrate group of Navicula, 

 many of them new. 



Plate III. contains 34 figures, of the N. Hennedeyi type. The 

 figures in these plates are the best I have ever seen. I would 

 particularly call attention to the following examples : — N. genifera 

 (? gemmifera), N. Kittoniana, N. inhalata, N. diffusa, iV. Hennedeyi, 

 N. spectahilis, N. pixetexta and its varieties. 



Plate IV. contains 24 figures of Surirellte of the Fastuosa type, 

 most of them admirably executed. 



In a letter from the author he informs me that in Part II., pi. 5, 

 the N. humerosa group will be given, in pi. 6 the N. Smithii forms, 

 (plates 9 and 10) will contain 152 figures of Cymbellfe, to be 

 followed by the Diploneis group, and then the Campylodisci, after 

 which he will probably take in hand the Ampliorce. This genus 

 will probably take six plates to illustrate it. 



Each part is accompanied by an index to the figures, which, 

 however, only gives the generic and specific names and localities, 

 but ultimately a more complete and perfect one will be given, in 

 which will be embodied the necessary corrections in nomenclature, 

 synonyms, &c. As this work is undertaken by the author without any 

 hope of profit, it is desirable that the cost should be covered by the 

 subscriptions, and we hope that those interested in the study of 

 these remarkable organisms will become subscribers.* The sub- 

 scription is six marks ( = six shillings) per part. After the pub- 

 lication of the fourth part it will be advanced to nine marks, one 

 part to be published every two months. 



F. KiTTON. 



N.B. — The second part has been issued since this notice was in 

 type. 



* Mr. Hardwicke, publisher, 192, Piccadilly, is the agent for England. 



