KONGL. SV. VET. AKADEMIENS HANDLINGAE. BAND 26. N:0 2. 67 



line. If this form does not belong to Caloneis, it is a Pinnularia, and is then akin to P. lo- 

 bata and P. excellens. 



73. C? Hardmaniana Cl. V. Sp. — V. deeply constricted, with subelliptical segments, 

 broadest at the base. L. 0,05; B. 0,oi6, at the constriction 0,oo5 mm. Median line with approximate 

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

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

 the ends, smooth. Longitudinal lines indistinct. — PI. YI f. 10 (Part II PI. I f. 10). 



Marine: Campeachy Bay (Hardmans coll.)! 



This species is akin to C. scintillans and may perhaps be a Pinnularia. 



Additional. 



74. C. latevittata Pant. (1893). — V. with parallel margins and cuneate ends. L. 0,o84; 

 B. 0,00 24 mm. Axial area narrow, slightly dilated around the central nodule. StriiB parallel 

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

 than to the median line. — Nav. latev. Pant. Ill PL VIII f. 122. 



Habitat? Hungary, Bodos (Pant.). 



I have not seen this species, and am uncertain whether it is a Caloneis or a Neidium. 



Neidium Pfitzer (1871). 



Valve elongated, linear 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 interior of the valve, and are divided by iissures parallel to the axis of the cell 

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

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

 p. 92 PI. II B 1855. — Db Bary, Bot. Z. Beil. p. 62, 1858). 



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

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

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

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

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

 a characteristic yellow colour. The strife are coarsely, or at least distinctly, punctate and they 

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

 or less regular, longitudinal strise. 



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

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

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



The numerous forms included in Neidium are so intimately 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 Griffith that the mother-cells of the auxospore have 

 rostrate, but the 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. 



