Okeden, on Diatomacecs. 
89 
genuinely new^ and admitted as such into the standard works 
on the subject — or as being interesting varieties of the more 
known species ; and also to the doubtful forms, the position 
of which has yet to be determined. Taking them therefore 
in the order in which the numbers of the slides run, they are 
as follows : 
No. 9. I give this as containing a curiously distorted form 
of Surirella biseriata, having a central construction ; this 
does not appear to me a common variety, as I have only once 
met with it. 
No. 10. I give as being my original gathering of Surirella 
apiculata, first pointed out by me to the late Professor 
Smith in April, 1854. I have never found it since, and I 
am inclined to agree with him when he terms it a close 
ally, if not a variety, of S. angusta." (Page 88, vol. ii, 
' Synopsis'.) 
Nos. 19 and 19 a. This is my original gathering of that 
curious species Orthosira mirabilis, and was first obtained by 
me at Haverfordwest, in April, 1855. In the April of 1857, 
I made a second and more copious gathering from the 
same spot; this will be found in No. 129. It has since 
been found by Mr. Ralfs and others, in the interstices of the 
barks of various trees. The Navicula in these gatherings I 
at first referred to N. tumida, but was corrected by the late 
Professor Smith, who pronounced it to be N.pusilla, and in this 
he is also supported by my kind friend and correspondent Dr. 
Walker- Arnott, I must, therefore, bow to such authority and 
name it as N.pusilla, but then the characteristic of "bracldsh" 
must for the future be omitted in giving the habitat of this 
species in any specific description, as the locality where this 
gathering was made was purely a fresh- water one, and totally 
free from marine or brackish influence. 
Nos. 29 and 59. In these two slides will be found a 
Pinnularia with somewhat constricted ends, which I consider 
as a variety P. radiosa. I see nothing to warrant the erec- 
tion of them into a new species ; I therefore merely point 
them out as an interesting variety of the above. A reference 
to the catalogue of the slides will, however, show that the two 
gatherings are from two widely diflerent localities ; thus we 
may assume that the variety is a well marked one. 
No. 35. I merely point this gathering out as being inter- 
esting from consisting of Synedra radians in a state of con- 
gregation, as shown in plate b, vol. 2, of Synopsis' ; of course 
the boiling in acid has destroyed the gelatinous envelope, but 
the bundles still remain perfect. 
Nos. 49, 50, 51, 52, and 53. I give these as affording ex- 
