Biatomaeex from the Caspian Sea. By A. Grunow. 683 



Var. ? abludens Grun. Valve linear lanceolate, not sigmoid. 

 Length, '155 mm.; breadth, "008 mm.; keel puncta, 

 3-4^; transverse striae, 22 in '01 mm. 



To the Nitzschia Sigma group belong the following species of 

 Homoeocladia. 



H. Kotschyi Grun. Valve, '22 mm. long, "007 mm. broad; 

 keel puncta, 7-7^ ; transverse strife, 24 in • 01 mm. ; connecting 

 zone with strong longitudinal striae. Salt Lake Atchin Ghol 

 (%. Kotschy), growing singly and in tufts. 



H. siihcohwrens Grun. Valve, "03- "045 mm. long, '004 

 broad; keel puncta, 9-10; transverse striae, 33-34 in -01 mm., 

 forming slight, delicate, and frequently ramifying threads, without 

 a definite integument. China, Bengal. 



Herr Frauenfeld gathered a similar form in Leith, Scotland; 

 it was partly in single frustules and partly in bushy tufts. 



LiCMOPHOREiE. 



Licmoiohora jidbellata Ag. Kg. Bac. tab. 12, figs. 1, 2, 4 ; 

 W. Smith, B. D. tab. xxxii. fig. 234. 



Var. ? gracillima Grun. Frustules shorter and narrower 



(•101 mm, long, '009 mm. broad); in the upper part 



linear, the lower cuneate. Bare. 



I have never seen this form in a living state, but only in 



single frustules. I have also seen no front view, and am therefore 



unable to decide whether it is allied to L. Remus or L. Romulus. 



COSCINODISCE^. 



Cyclotella Casjpia Grun. — C. minuta, margine tenuissime striate, 

 centro undulato, irregulariter punctato. Diam. "18 mm.; latit. 

 marginis, -004 mm.; strife radiantes, 21 in -01. 



Not uncommon in the Harbour of Baku. 



Approaches most nearly to C. opercuJata Kg., but is dis- 

 tinguished by the absence of marginal puncta (spines?) and by 

 its delicate striae. I reckon as Cyclotella? only those forms with 

 sharply-defined radiating marginal striae. To distinguish the 

 species requires great caution. G. operculata has a strongly 

 striated margin (striae l(j-17 in "01 mm.). 



G. antiqua W. Sm. is closely allied to G. operculata. It is 

 distinguished by the presence of large triangular excavations near 

 the centre. I have observed many transitional forms in G. 

 operculata var. radiosa. 



To the large forms of G. operculata is allied a Cyclotella, which 

 Euleustein found in the Bodensee (Lake Constance) and named it 

 G. Bodanica, and which I also have seen in soundings from the 

 Traunsee (Lake of Gmunden) . 



The largest were "OO mm. in diameter, with broad (-015 mm.) 



