90 Okeden^ on DiatoMace(e.' 
cellent samples of Navicula firma, and its varieties. First in 
Nos. 50 and 51^ we find the true N. firma j with the valve 
truly elliptical_, and slightly attenuated towards the rounded 
extremities next, in No. 53, we have the variety with the 
ends " suddenly attenuated;" next, in No. 49, we have the 
variety y (page 90, vol. ii,^ Synopsis^), with the ends '^'^curvate,'' 
a much larger form than any of the preceding, and vdth 
coarser; and lastly, in No. 52, we shall find (if carefully 
looked for) an intermediate variety between /3 and y, namely, 
one in which the ends are slightly constricted, while the very 
apices of those ends are cuneate. I may add also, that No. 
49 abounds in fine specimens of Suynrella biseriata, while in 
No. 53 will be found, though rare, good specimens of Dr. 
Gregory^ s Surh'ella tenera — S. linearis of the ^ Synopsis\ 
No. 67. I give this slide as containing a curious variety of 
Diato?na elongatum, for I can refer it to no other species. I 
allude to the small form in the slide, the side view of which 
shows a central inflation ; in fact, in outline it much resembles 
the S.V.of Navicula inflata, for which it might be mistaken, did 
not a careful examination of the slide show the frustules, grow- 
ing in the zigzag chains, characteristic of the genus Diatoma. I 
have marked one of these chains with an ink ring, to facilitate 
the examination of any member interested in the matter. I 
give this doubtfully as a variety of the above species (D. 
elongatum), for in many respects it must be confessed, it 
widely differs from the specific description of that species in 
the ' Synopsis^, (see vol. ii, page 40.) The description there given 
says " Valve linear extremities slightly inflated ;" and again, at 
page 41, in describing the difference between D. grande and 
D. elongatum, the author says, "In D. elongatum the ex- 
tremities in the mature valve are absolutely wider than 
any other portion of the valve." But in the Diatoma under 
consideration, it is the centre which is inflated and wider 
than any other portion of the valve. Still I see not sufficient 
grounds at present for erecting it into a new species, and I 
therefore leave it for future observers as a (?) variety of 
B. elongatum. 
No. 69. I merely draw attention to this as being a fine 
gathering of Nitzschia plana, by no means a common species ; 
Tryblionella scutellum also occurs here, though rarely. 
No. 85. I would draw attention to this as being a fine 
gathering of that rare Diatom, Nitzschia scalaris. Up to the 
present time I am not aware of any other habitats for it 
except Poole Harbour (the original one), and the Haverford- 
west Salt Marshes, in which this gathering was made in 1856. 
Allusion is made to it by the late Professor Smith, in his 
