NOTES AND MEMORANDA. 
357 
the following note : — In my remarks on this form in the previous 
number (p. 239), I find I am mistaken in supposing that there were no 
objectives of sutficient defining power to resolve the Californian Hyalo- 
discus {H. Franklinii) when Professor Bailey published his species. 
In his ‘Notes on some new Test Objects’ he mentions objectives 
made by Spencer, and Powell and Lealand, capable of resolving tests 
as difficult as the markings on H. Franklinii. 
Schmidt's Atlas der Diatomaceen-Kunde. — Mr. Kitton also kindly 
contributes the following : — The long delay in the publication of 
])arts 15 and 16 has arisen from the continued illness of the author. 
We are glad to say that he is now recovering, and he hopes to be able 
to publish the future parts with greater regularity. 
The parts just received are devoted to that very puzzling genus, 
Coscinodiscus, of which 218 figures are given. The majority of them 
are excellent delineations, and can be easily recognized. 
We think that too many figures of one sj)ecies are given, the 
differences being much too slight even to constitute varieties ; for 
example, C. suhtilis, which differs but little from G. fasciculatus (by the 
way, the Kev. E. O’Meara describes and figures a species under this 
name in the ‘ Q. M. J.,’ vol. vii., N. S., p. 249, pi. vii. f. 1, but it is 
not the same as Schmidt’s species. He afterwards, in his ‘Irish 
Diatoms,’ refers it to C. Normanii of Greville, which does resemble 
Schmidt’s C. fascicidatus, but which certainly does not resemble 
O’Meara’s). C. curvatulus is probably only a variety of 0. suhtilis. 
Greville’s C. symmetricus is simply distinguished by its larger granules. 
C. extravagans must be referred to Aulacodiscus if the generic cha- 
racters of that genus are of any distinctive value. Judging from the 
figure, we should be disposed to think it an immature valve of A. 
Oregonus. Fig. 34 (unnamed) is no doubt also a member of that genus, 
as the author surmises. C. cocconeiformis is a very doubtful Coscino- 
discus ; it approaches very near to Cocconeis superha^ J anisch, the prin- 
cipal difference being its circular outline, a distinction of little value. 
C. denarius closely resembles C. Barhadensis of Greville.^ 
Part 16 contains many admirable figures of the large-celled Cosci- 
nodisci ; many, however, appear to us to have no claim to be considered 
distinct species or even varieties. C. hulliens is the form usually 
considered by English diatomists to be the true C. heteroporus of 
Ehrenberg. 
In this part we have 67 figures, of which only 18 are named. 
C. rohustus, Greville, is probably the same as C. marginatus, Ehr. 
We have in previous notices of this work expressed our regret that 
so many figures are given to illustrate differences which are of no 
specific value. As our knowledge of these forms increases, we see that 
characters that were once considered to be good specific or generic 
distinctions, are now valueless. We have Triceratia that are circular, 
Coscinodisci with three and four sides, and Pleurosigmas perfectly 
straight. 
* ‘ Trans. Mic. Soc.,’ vol. ix. p. 45. 
