132 p. T. CLKVb:, .SYNOIVSKS OF THE NAVICl LOlI) DIATOMS. • 



Var. Radiila Cl. — V. in L. 0,i4, in B. 0,o2i mm. Striiu 12 in U,ui mm.; puncta 9 

 in 0,0 1 mm. 



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



o. A. spectahilis (tREo. (]S,'')7). — Frustule elliptic-rectangular. L. n,M; B. (),o.^) mm. 

 Zone finely tran.sversely striate; stria' ahout 12 in 0,oi mm. finely punctate. V. narrow. L. (),o7 

 to 0,14; B. 0,0:2 mm. linear, with obli([ue]y rounded ends. Striie on the dorsal side of the valve 

 5 to () in 0,0 1 mm., furcate, composed of coarse pnncta, about 14 in Hjn imn. Stria- on the ventral 

 part 8 to {) in 0,oi mm. - i). of Clyde p. 51() PI. Xlll f. 80 a and r. A. S. Atl. XL f. 18 to 23. 

 A. furcata Leud. Fortm. D. de Ceylon p. 20 PI. 1 f. IJ (1879). 



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

 Samoa! We.st Indies! Davis Straits! Macassar Straits! 



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

 the fig. a and d, but h 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. O.od 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'. Stritie ^,h in 0,oi 

 mm., curved and compo,sed of puucta, about 8 in (),oi mm. Ventral stria? divei'gent on the portion 

 between the central and terminal nodules. — Diatomiste I p. 157 PI. XXll 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 stria^ are coarse, 1 believe it is more 

 nearly related to A. ohtusa than to A. urenaria. 



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 striai on the dorsal and ventral 

 .side of the valve. 



This subgenus, named after one of the typical species, A. arcnaria 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 Sfanroncis, and the non-complex Mierosti<jni<itic(P are pro- 

 bably in near relation to this section. 



Artificial key. 



. i Central nodule dilated to a staiu'os 2. 



\ - - not - - - 4. 



( Puncta arranged in deenssating stri;e • . . . . .1. Flcurnsifjiiia Temp. a. Brun. 



2. ■! — • — — transverse — 4. 



I — indistinct A. hia)i,s Flogel. 



j Marine species A. ocellata Donk. 



\ Fresli water species A. delphinea A. S. 



. J Marine species 5. 



\ F'resh water species A. Bcrggrenii Cl. 



^ I Valve not inflated or with a single median inflation A. arenaria Donk. 



\ — with two median inflations A. higgibosa Cl. 



