Okeden^ on Diatomacece. 
91 
paper on the Pyrenean Diatoms, in the ' Magazine of Natural 
History/ for January, 1857. 
No. 92. In this gathering will be found rather plentifully 
a minute oval form, with median line, which I give doubt- 
fully as (?) Achnanthidium lineare. The side views are the 
most abundant, but a careful examination of the slide will 
detect the F. views, which exhibit decidedly the geniculate 
character of the genus. As the present gathering has never 
been treated with acid, does not exhibit stripes, and did not 
do so even when fresh gathered, I place the form in question 
with the genus Achnanthidium. I refer it doubtfully to A, 
li7ieare, because a careful examination will show that it does 
not entirely agree with the specific description of that specie 
in the ' Synopsis,' and thus I leave it for other observers. 
Nos. 99 and 1?9«. In this gathering will be seen somewhat 
plentifully a small, elliptical, lanceolate form, with an appa- 
rent stauros, but the application of a sufficiently high power 
will show that there is no true stauros, and that the striae 
extend over the whole surface of the valve. It is the Stau- 
roneis dubia of Dr. Gregory, and is allied to his Stauroneis 
rectangularis (now Navicula Icevissima of the ' Synopsis,' 
vol. ii, p. 91). For the reasons above stated, however, its 
removal from that genus becomes imperative, and it must 
follow his Stauroneis i^ectangularis into the genus Navicula. 
Adopting the suggestion of my friend Dr. Arnott, I propose 
to name it Navicular decipiens. 
No. 102. In addition to the Nitzschia Closterium in this 
gathering, will be found a small form which I refer doubt- 
fully to the frustules of a Schizonema. The valve is laure- 
stale, acute on side view, and linear on F. view. When 
gathered fresh, the frustules were certainly free ; yet a pecu- 
liar arrangement of them, in which they appear to be con- 
gregated into something approaching to a filamentous state, 
leads me to suppose them to be the produce of a Schizonema, 
either broken loose or preparing to throw ofi" the mucus 
which is to form their envelope. 
Nos. 104 and 104a. In this gathering will be seen two Syne- 
drse, one an extremely long form, with rather coarse striae, 
which I refer to Synedr(B longissima ; the other, a shorter and 
more slender form, with more delicate striae, I am inclined to 
refer to S. radians, var. y. A better and purer gathering of 
the S. longissima will be found in No. 146, from Tenby ; I 
think it cannot for a moment be confounded with S. radians. 
Nos. 107 and 107«. Are worth notice for a curious small 
form of Pi^inularia interrupt a, which is abundant in them. 
No. 109. I give this as the true Cocconema parvum, not a 
