12 p. T. CLEVE, ON SOME NEW DIATOMS. 



19. Navicula arnica Cl. et Grun. 



Contracted in the middle, ends cuneate; stria? 7V2 in 0,01 mui., almost parallel, 

 smooth. The two interior rows of striaj are interrupted in the middle. 

 Length 0,075 mm. Breadth 0,023 mm. 



PI. Ill, fig. 37, "'7,- 

 Tahiti (Eugenie Exp.). 



20. Navicula quadriseriata Cl. et Grun. 



Large, oblong oval with parallel sides and cuneate ends. Stria; smooth, 8 in 0,01 

 mm. in four longitudinal, uninterrupted rows. The interior striaj are shortened around 

 the central nodule, which is surrounded by an orbicular area. 



Length 0,09 mm. Breadth 0,035 mm. 

 Pl.III, fig. 32, %. 



Balearic Islets very rare (F. Soderlund). 



Two other species, of which Mr. Grunow has sent me figures, seem to be related 

 to the last described forms: N. Castracanei Guvi!i. (PL III, fig. 33, "7i) and JSf. Petitiana 

 Grun. (PI. Ill, fig. 34, '7i)- Both species are elliptic lanceolate and have the interior 

 rows of stria) parallel with the margins of the valve, not close to the median line. 

 N. Castracanei is 0,1 mm. in length, 0,03 mm. in breadth, and has 9 stria; in 0,01 mm. 

 N. Petitiana is 0,07 mm. in length and 0,02 mm. in breadth and has 11 stria; in 

 0,01 mm. 



All these species together with the following seem to form a section, for which 

 Mr. Grunow has proposed (Cl. et Grun. Art. Diat. pag. 29), the name quadri-seriatce : 

 This group contains: 



Navicula Powellii Lewis N. Vidowichii Gkun. 



N. Egyjitiaca Grev. 



N. {Powellii var.) Gallapagensis Cl. 



JV^. Zanardiniana Grun. 



N. Wittii Grun. 



N. arnica Cl. et Grun. 



N. quadriseriata Cl. et Grun. 



N. Castracanei Grun. 



N Petitiana Grun. 



? N. {Stauroneis) robusta Petit (Diat. de Tile Campbell PI. V, fig. 16). 



N. biseriata Petit (1. c. PL IV, fig. 15). 



N. Richardsoniana O'Meara (Irish Diat. PI. 31, fig. 33). 



N. Eugenice Cl. (this paper pag. 7). 



? N. denticulata O'Meara (Quart. J. M. S. VII, p. 115, PL V, fig. 2, 1867). 



? N. Musca Ehb. 



? N. mirabilis Leuduger Fortmorel (Diat. de Ceylon PI. II, fig. 21). 



N. blanda A. Schm. (Nordsee Diat. PL II, fig. 27). 



N. latefasciata Grun. (in Cl. et Grun. Arct. Diat. PI. I, fig. 21\ 



