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



Var. Radula Cl. — V. in L. 0,i4, in B. O, (321 mm. Strite 12 in 0, 01 mm.; puncta 9 

 in 0,01 mm. 



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



3. A. spectabilis Greo. (1857). — Frustnle elliptic-rectangular. L. 0, 1.1; B. 0,o5 mm. 

 Zone finely transversely strlate; stricB abont 12 in 0, 01 mm. finely punctate. V. narrow. L. 0,o7 

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

 5 to (5 in 0,01 mm., fnrcate, composed of coarse puncta, about 14 in 0,oi mm. Stri?e 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. furcata Leud. Fortm. D. de Ceylon p. 20 Pl. I f. 11 (1879). 



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

 Saraoa! 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 

 Ä. obtusa. 



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

 ventral margins, and obtuse, broad ends. L. 0, 09 to 0, 1 67; B. 0, 03 to 0, 07 mm. Components of 

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

 mm., curved and composed of puncta, about 8 in 0, 01 mm. Ventral strite 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 strite are coarse, I believe it is more 

 nearly related to A. obtutia than to A. urenaria. 



Subgenus Psammamphora Cl. 



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

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

 tudiiial lines. Structure tine puncta disposed in transverse rows or strirE 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 chaTacteristie of generic value. It is well defined, and closely 

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



Araong tlie Naviculas the group Staiironciv, and the non-complex Microstujmaticce are pro- 

 bably in near relation to this section. 



{ 



Artiftcial hcy. 



Central nodule dilated to a stauros 2. 



— — not — — — 4. 



[ Puncta arrangcd in decussating stria' ■ . . . . ,4. Plewosignui Tkmp. a. Brun. 



I — — — transverse — 4. 



I — indistinct A. Mans Flögel. 



) Marine sijeeies A. occllata Donk. 



1 Fresli water species A. delphinca A. S. 



j Marine sjjecies 5. 



\ Frosh water species A. Bcrynrcnii Ci.. 



Valve not inflated or with a single median inflation A. arcnaria Donk. 



with two median inflations A. biggibosa Cl. 



( Valve 



