KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. I8. N:0 5. 13 
subdivisa Grun. (Nordsee Diat. fig. 20). 
consimilis A. Scum. (1. c. p. 46). 
emula Grun. (in A. Scum. Nordsee Diat. II, fig. 47). 
superimposita A. Scum. (Nordsee Diat. TH, fig. 34 and Diat. Atl. Pl. 46, 
fig. 61). 
To these species are two undescribed forms nearly allied: N. Bruchit Grun. 
and NV. multiseriata Gru. ° 
N. Bruchit Grun. (Pl. II. fig. 35, °°°/,) found on Tahiti, is in length 0,04 mm. 
and in breadth 0,012 mm. 
N. multiseriata Grun. (PL UI, fig. 36, °°°/,) from Tongatabu, is in length 0,036. 
Navicula. Section: Pseudo-amphiprora Ct. 
I propos¢ to include in this section a small number of Navicula-forms, which 
are in some respects akin to Amphiprora and in other to Stauroneis. The valve on 
both sides in the median line is divided by a.keel into two portions. The central no- 
dule is transversely dilated into a short stauros, reaching the above named keels. The 
type of the section is: 
Navicula arctica Cu. 
In my paper On the arctic Diat. (Bih. till K. Sv. Vet. Ak. Handl. 1873, 1, 
N:o 18, p. 16, Pl. III, fig. 18). 
This fine species was first described and somewhat indifferently figured by Bamay 
(Smirus. Contr. Vol. VII, p. 8. fig. 14 and 15, 1853) as Amphora stauroptera. GRE- 
Gory afterwards gave (in his Diat. of Clyde 1857, p. 34, Pl. IV, fig. 59¢.) a very fine 
figure of the species in question in S.V., but he regardes it as Amphiprora lepidoptera. 
At the same time he describes the F. V. as Amph. obtusa (fig. 60 l.c.). but Mr. Lacrr- 
sTeDT (Bih. till K. Sv. Vet. Ak. Handl. T. III, N:o 15, p. 46) has found that the two 
figures (59 and 60) belong to the same species. As the names N. stauroptera and N. 
obtusa have been used for other forms it will be most conveniant to name the species 
N. arctica. A. Scumipt has figured the species in his Nordsee Diat. Pl. II, fig. 1 as 
Amphiprora obtusa Gree. If the Nav. arctica O'Meara (Micr. Journ. Vol. XIV, PI. 
VIII, fig. 1) belongs to this species I d’ont know. 
The Nav. arctica lives in the northern part of the Atlantic. It has been issued 
in Cr. et Moz. Diat. N:o 57. 
21. Navicula jugata Cu. 
Elegantly elliptic with parallel, indistinct, and punctate strie, 10 in 0,01 mm., 
between the keels and the margins. The median portion of the valve, between the 
keels, seems in very oblique light and with good objectives to be exceedingly finely 
striate. 
