134 



V. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



5. A. delphinea (Bail. 1861?) A. S. Atl. (1876). — Frustule silicious, broadly elliptic-rec- 

 tangular, frequently gibbous in the middle. L. 0,076 to 0,12; B. 0,05 to 0,068 mm. Valve linear 

 to lunate, with obliquely rounded ends. Central nodule dilated to a stauros. Terminal fissures 

 deep. Striee 27 to 28 in 0,oi mm., on the dorsal side parallel, on the ventral divergent towards 

 the median line. — Bost. Jour. Nat. Hist. VII PI. I f. 1 (fide H. L. Sm.). A. S. Atl. XL f. 26, 27. 



Eresh water: Lemerara River! 



Var. minor Cl. — V. in L. 0,06; B. 0,012 mm. Striae 24 in 0,01 mm. — A. S. Atl. XL f. 25. 



Fresh water: North America, Crane Pond! Demerara River! 



Var. jamalinensis Cl. a. GtKun. (1880). — V. more linear, with gibbous middle. L. 0,04 8 to 

 0,057; B. 0,01 to 0,011 mm. Striae very fine. — A. ocellata var. jamal. A. D. p. 24 PI. I f. 6. 

 A. S. Atl. XL f. 24? 



Brackish water: Sea of Kara! Pensacola (Atl.)? 



It is difficult to find any specific distinction between this species and A. ocellata. Yet they 

 cannot be regarded as the same species. A. o'cellata is thinner, has somewhat coarser striae, and 

 less deeply impressed terminal fissures. Moreover A. delphinea is a freshwater form and A. 

 ocellata marine. 



6. A. Berggrenii Cl. (1878). — Frustule silicious, subrectangiilar with rounded ends. 

 L. 0,06 5; B. 0,0 2 5 mm. Median line with distant median pores; its terminal fissures deep and 

 flexuose. Central nodule not dilated into a stauros. Dorsal striae parallel, 17inO,oi mm., ventral 

 striae divergent towards the median line. — Cl. a. M. D. N:o 90. Cl. N. R. D. p. 4 PI. I f . 8 

 (1881). H. L. Sm. T. N:o 610. 



Fresh water: New Zealand, Arthur's Pass, foss. ! 



This remarkable species is evidently akin to A. delphinea, although its central nodvile is 

 not dilated to a stauros. 



7. A., hiaiis Flogbl (1873). ^ Frustule elliptical, in the middle slightly constricted, with 

 truncate ends. L. 0,045; B. 0,oi5 mm. V. narrow with slightly reflexed ends. Central nodule a 

 transverse stauros. Striae not seen. — Pommerania Exp. p. 88 f. 7. 



Marine: Knarrhoi, Kattegat (Flogel). 



with cell 



a var. ventricosa 

 contents; 600 times 

 magnified. 



Subgenus Cymbamphora. 



Valve narrow elongated, semilanceolate, gradually tapering from 

 the middle to the acute or subacute ends. Median line straight, approxi- 

 mate to the ventral margin. Striae not crossed by longitudinal lines. 

 Connecting zone witliout divisions. — Living specimens of A. angusta 

 var. ventricosa have a chromatophore-plate along the ventral side of the 

 connecting zone. Another plate occurs on the dorsal side. Both are 

 deeply constricted in the middle. 



This subgenus, in which the valves have a considerable likeness 

 to some Cymbellae, comprises marine forms only, so closely connected that 

 many of the reputed species difi'er in nothing but the number of striae, 

 size of the valve, and such trifling characteristics. 



Artificial hey of species 



I Striae very fine 20 or more in 0,0 1 mm 2. 



\ — coarser less than 20 in 0,01 mm 3. 



_ J Frnstnle short, narrow elliptical A. cymbelloides Grun. 



\ — very elongated, linear A. arcta A. S. 



