132 p. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Var. Eadula Cl. — V. in L. 0,i4, in B. 0,o2i mm. Striae 12 in 0,oi mm.; puncta 9 

 in 0,01 mm. 



Marine: Gulf of Naples (Petit and Deby Coll.)! 



3. A. spectabilis G-eeg. (1857). — Frustule elliptic-rectangular. L. 0,i4; B. 0,o5 mm. 

 Zone finely transversely striate; strise about 12 in 0,oi mm. finely punctate. V. narrow. L. 0,o7 

 to 0,14; B. 0,02 mm. linear, with obliquely rounded ends. Striae on the dorsal side of the valve 

 5 to 6 in 0,01 mm., furcate, composed of coarse puncta, about 14 in 0,oi mm. Striae on the ventral 

 part 8 to 9 in 0,oi mm. — D. of Clyde p. 516 PL XIII f. 80 a and c. A. S. Atl. XL f. 18 to 23. 

 A. fiircata Leud. Forth. D. de Ceylon p. 20 Pi. I f. 11 (1879). 



Marine: North Sea! Mediterranean Sea! Ceylon! Borneo! Seychelles! Madagascar! China! 

 Samoa! "West Indies! Davis Straits! Macassar Straits! 



The description of this species in D. of Clyde agrees very well with this species, as do also 

 the fig. a and d, but b and c belong probably to another species and fig. e seems to represent 

 A. ohtusa. 



4. A. obesa Cl. and Grove (1892). — V. with almost semicircular dorsal, and straight 

 ventral margins, and obtuse, broad ends. L. 0,09 to 0,i67; B. 0,o3 to 0,o7 mm. Components of 

 the median line divergent from the central nodule at an angle of about 140'. Striae 9,5 in 0,oi 

 mm., curved and composed of puncta, about 8 in 0,oi mm. Ventral striae divergent on the portion 

 between the central and terminal nodules. — Diatomiste I p. 157 PL XXII f. 8. 



Marine: Macassar Straits! 



Of this curious form valves only are known at present, so it cannot be decided whether it 

 belongs to Amblyamphora or Psammamphora, but as the striae are coarse, I believe it is more 

 nearly related to A. ohtusa than to A. arenaria. 



Subgenus Psammamphora Cl. 



Frustule more or less rectangular. Connecting zone not complex. Median line arcuate. 

 Central nodule frequently transversely dilated to a stauros. No axial or central areas. No longi- 

 tudinal lines. Structure fine puncta disposed in transverse rows or striae on the dorsal and ventral 

 side of the valve. 



This subgenus, named after one of the typical species, A. arenaria Donk., comprises forms 

 with or without stauros, which is no chaTacteristic of generic value. It is well defined, and closely 

 analogous to the subg. Amhlyamphora, the zone of which is complex. 



Among the Naviculas the group Stauroneis, and the non-complex Microstigmaticce are pro- 

 bably in near relation to this section. 



Artificial key. 



^ i Central nodule dilated to a stauros 2. 



\ — — not — — — 4. 



{Puncta arranged in decussating striae ' . . . A. Pleurosigma Temp. a. Brun. 

 — — — transverse — .4. 



— indistinct A. Mans Flogbl. 



Marine species . . . . . A. ocellata Donk. 



Fresh water species A. delphinea A. S. 



. / Marine species 5. 



\ Fresh water species . . A. Berggrenii Cl. 



J Valve not inilated or with a single median inflation A. arenaria Donk. 



\ — with two median inflations A. biggibosa Cl. 



c 



