KONGL. SV. VET. AKADEMIENS HANDLINGAR. HAND 26. .N:() 2. 67 



liue. If this form does not belong to Caloneis, it is a Pinmilaria, and is then akin to F. lo- 

 bata and P. excellens. 



73. C? Hiirdniauiaiiii Cl. V. Sp. — V. deeply constricted, with subellijitical segments, 

 broadest at the base. L. O, os; B. (),oi6, at tlie constriction 0,oo.i mm. Median line with approximate 

 median pores, and small terminal nodnles. Axial area very broad, elliptical in each segment. 

 Central area a broad, transverse fascia. Strise. 8 in 0,oi mm. at the base of the segments, 10 at 

 the ends, smooth. Longitudinal lines indistinct. — Part II Pl. I f. 10. 



Marin e: Campeachy Bay (Härd mans coU.)! 



This species is akin to C sciutillans and may perhaps be a Pinmilaria. 



Additional. 



74. C. latevittata Pant. (1893). — V. with parallel margins and ciineate ends. L. 0,084; 

 B. 0,0024 mm. Axial area narrow, slightly dilated around the central nodule. Strite parallel 

 throughout, 18 in 0,oi mm. not distinetly punetate. Longitudinal lines broad, nearer to the margin 

 than to the median line. — Nav. latcv. Pant. III Pl. VIII f. 122. 



Habitat? Hiingary, Bodos (Pant.). 



I have uot seen this species, and am uncertain whether it is a Caloneis or a Neidium. 



Neidium Pfitzek (1871). 



Val ve elongated, liuear to broadly lanceolate. Median line straight; its central pores turned 

 in contrary directions; its ends with two lateral and one axial prolongations. On both sides of 

 the median line are one or two longitudinal lines. Axial area narrow or indistinct. Central area 

 orbicular or somewhat transversely dilated. Structure: distinct puncta, disposed in transverse, 

 usually oblique, rows. Cell-contents: two chromatophores along the connecting zone, which do not 

 migrate along the interiör of the valve, and are divided by fissures parallel to the axis of the cell 

 (Pfitzer, Bau und Entw. p. 39). In conjugation two cells form two auxospores with transversely 

 striate perizonium, which opens by an operculnm (Griffith, Ann. and Mag. n. hist. s. 2 Vol. XVI 

 p. 92 Pl. II B 1855. — De Baby, Bot. Z. Beil. p. 62, 1858). 



The genus Neidium was founded in 1871 by Pfitzer (Bau u. Entw. p. 39) on the charac- 

 teristics of the cell-contents, but the peculiarities of the valve are also sufRcient for the distinction 

 of Neidium as a genus. The median line has the central pores turned in contrary directions. Tlie 

 terminal nodules are also peculiar. The longitudinal lines point to some relation between Neidium 

 and Caloneis, but the structure is difierent. The forms of Neidium have in the dry state usually 

 a characteristic yellow colour. The striaj are coarsely, or at least distinetly, punetate and they 

 usually cross the valve in an oblique direction. Tlie puncta form also, on the other hand, more 

 or less regular, longitudinal stritB. 



Neidium is, as far I can see, not uearly akin to any other genus, although there are some 

 relations to Caloneis, of which genus C. Silieula was by Pfitzer included in Neidium. One species 

 of Scoliopleura, viz. S. Schneideri CtRUN. resembles Neidium in the oblique striation. 



The numerous forms included in Neidium are so intimatelj' connected, that all the species 

 are more or less artificial and founded on variable characteristics, such as the form and outline of 

 the valve. It seems from the observations of GtRIFFITh that the mother-cells of the auxospore have 

 rostrate, but tlie young cells, rounded ends. Strictly speaking, perhaps all the forms of Neidium 

 ought to be treated as varieties of one species, but this course would make it difficult to dis- 

 criminate between the numerous forms. 



All the Neidia live in fresh water, some few also in brackish water. They occur in arctic 

 as well as in tropical regions. 



