20 P. T. CI.EVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Ärtificial key. 



I Valve more or less boat-sliajied 2. 



) — — — reniform 4. 



I Stri» 10 to 11 ill 0,01 mm Ä. coarctata Be. 



\ — 20 to 22 - a. 



( Zone with a few larger stigmas A. pulchra Geev. 



\ — witliout stigmas Ä. dccipiens Gkun. 



Keel strongly inflected in the middle 5. 



not, or slightly, inflected 6. 



I Keel 



J Striffi 15 to 16 in 0,0 1 mm A. intermedia Lewis. 



1 Strise very fine A. insecta Geun. 



J Striffi transverse 8. 



\ — curved, divergent towards tlie median linc 7. 



Strise eoarse (IS in 0,oi mm.) A. Am2)hitritis Caste. 



— finer (20 in 0,oi mm.) . . • A. complcxa Gkeg. 



) Valve large (L. 0,17 mm.) .4. javanica Cl. 



\ — small (L. 0,oa to 0,03 ram.) A. minuta Cl. 



I 



1. A. (?; coarctata Brun (1889). — V. lanceolate, acute. L. 0,1 15 to 0,135; B. 0,02; Height 

 0,025, at the coiistriction 0,oi3 mm. Median line liiglily elevated between tlie central nodule and 

 tbe ends. Central area small, nnilateral. Junction-line between the keel and the lower part of 

 the valve very distinct, with a .sinns on eacli side of the central nodule. Strife 10 to 11 in 0,oi 

 mm., convergent on both sides of the central nodule, punctate, puneta 12 to 13 in 0, 01 mm. — 

 AmpMxJrora coarcf. Buxjn. D. foss. du Japon p. 14 Pl. Ill f. 12. 



Marine: Japan, fcssil and living (Brun)! 



A.s the entire frustule is not known, it is impossible to decide whether this species, which 

 has a great resemblance to a true Amphiprora, belongs to Auricula or to the sections Plagiotropis 

 or Amphitropis of Tropidoneis. The incompletety described Amji^ii^n-ora nitida Grev. (Edinb. 

 N. Ph. J. XVIII p. 40 f. 18, 1856) has some resemblance to A. coarctata, but has not a com- 

 plex zone. 



2. A. decipiens G-run. (1882). — Frustule quadrate to rectangular, slightl3' constricted in 

 the middle. L. 0,o(i to 0,ii; B. 0, 05 mm. Junction-line distinct, sinuose. Central area indistinct. 

 StricE 20 in 0, 01 mm., a little doser on the valve. Connecting zone, on the dorsal side, with broad 

 divisions, about 3 in 0, 001 mm., transversely striate; strifB 22 in 0, 01 mm. Divisions narrow on 

 the ventral side. — Aniphoropsis decipiens Grun. in Cl. M. I). N:o 309. V. H. Syn. Pl. XXII bis 

 f. 11. Amphiprora plicuta Greo. D. of Clyde p. 505 Pl. XII f. 57 (1857)? 



Marine, aestuaries: Scotland! 



3. A. pulchra Grev. (1863). — Frustule membranaceous, quadrate, slighth' eonsti-icted. 

 L. 0,075; B. 0,04 5 mm. Connecting zone with numerous divisions, about 5 in 0, 01 mm., transversely 

 striate; striee. about 22 in 0, 01 mm. On the zone, close to the valve, are 3 or 4 large isolated 

 stigmas. Valve with transversely dilated central nodule and elevated keel, bordei-ed with a row 

 of puneta, 6 in 0, 01 mm. Striaj 22 in 0, 01 mm. — Amphor a pulchra G('&ev . Edinb. N. Ph. J. XVIII 

 p. 184 f. 2. — Auricula pulc. Pl. Il f. 23. 



Marine: Queensland (Grev.)! China! .Macassar Straits (Grove coll.)! South Pacific Ocean (Van 

 Heurcks coll.)! 



The foUowIug incompletely described forms seem allied to this species: Amphiprora lincata 

 Grev. (Edinb. N. Ph. J. XVIIIp. 40 f. 19; 1863) and Amph. Jolisiaiia Grev. (1. c. p. 186 f. 11). 



4. A. insecta Grun. (1876). — Frustule membranaceous, globose. L. O.06 to 0,n ; B. 0, 04 

 to 0,0 5 mm. Median line strongly inflected towai'ds the centre of the frustule. Central nodule 



