76 
Transactions of the Royal Microscopical Society. 
unlock the mysteries of the diatom world. Alas ! the anomalies 
were so many and the difficulties so great, that I abandoned it in 
disgust.” 
Appended to the “ System ” is a list of Diatomaceae found by 
the author in the environs of Paris : these gatherings were mostly 
made during the cold and wet seasons, viz. in winter and early spring. 
From this list I select those forms of which M. Petit has given 
figures and descriptions ; a copy of his plate is also added. I may 
here remark that Fig. 1 c is not in the original plate, but has been 
reproduced from a sketch sent to me by M. Petit. — F. K.] 
Cynibella turgida (Greg.) var. /3 incisa Petit. This little 
variety I have found in only one locality near Marly ; it is distin- 
guished from the typical form by slight indentations on the ventral 
margin (Fig. 2, a, h). 
Navicula firma (Ktz.) var. S scoliopleuroides Petit. This 
species is remarkable for the disposition of the striae, which cut the 
median line obliquely as in the genus Scoliopleura ; the zone is also 
obliquely striated, as in the latter genus. Length, 107 g 8 ; 
breadth, 26 g 4 ; striae, 82 in 25 g. Ermenonville. In a piece of 
water in the centre of File des Peupliers. Tomb of J. J. Kousseau. 
( Fi g- !■) 
[Fig. 1 c represents a form of this species identical with Ehren- 
berg’s N. Iridis, as found in the Monticello (N. York) subpeat deposit, 
and which likewise has a similar obliquity of striation. “ Var. S ” 
must be deleted, as I have previously figured a var. S of N. firma. * 
Professor Pfitzer makes a new genus of the N. firma group, which 
he calls Neidivm : according to him, it differs from the Naviculese ; 
first, the endochrome layers are immovable, dividing whilst still on 
the zone ; second, that fission does not take place obliquely, but 
parallel to the longitudinal axis of the cell. f — F. K.] 
Stauroneis Cohnii Iiilse (Fig. 3). [The figure does not agree 
with Schumann’s ; t his is elliptical lanceolate, apices obtuse and 
slightly produced, the striae reaching the median line. — F. K.] 
Surirella patella Ktz. Marsh at de Presles. (Fig. 4.) [Pro- 
bably only a variety of S. ovalis. — F. K.] 
Campylodiscus noricus (Ehr.) var. /3 costatus (? Grunow). 
(Fig- 5.) 
Nitzscliia sigmoidea (Nitz.) var. /3 undulata, n. s. This variety 
is very abundant in the Marais de Ver. It is distinguished by the 
undulation of the keel. Length, 22 g 3 ; breadth, 8 g 8 ; puncta, 
14 in 25 g. (Fig. 6.) [This form is not var. /3 of the ‘ Synopsis,’ 
which is probably a distinct species and the same as Synedra 
spedabilis Ehr. ( N . spectabilis Pritchard, p. 72, 4th edit.). The 
undulations are not confined to the keel, the opposite margin is also 
* ‘ Science-Gossip,’ 18G7, p. 156. f Pfitzer, loc. cit., p. 39. 
J ‘ Die Diatomeen tier Hoheu Tatra,’ pi. iv. fig. 61 . 
