22 



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



accad dei n. Lincei 1873 p. 406 PL VII f. 2. Peragallo Villefranche D. p. 42 PI. II f. 18. A. Sson- 

 taghii Pant. Ill PI. VII f. 104 (1893). 



Marine: Marocco! Balearic Islands! Adriatic! 



To the genus Auricula may belong Aur. Grunowii Pant. Ill PL XXXI f. 453. Amiphiprortf, 

 striata Pant. Ill PL XXXIX f. 543 and AmpMprora Fethoi Pant. Ill PL XLI f. 565 all un- 

 known to me. 



Tropidoneis Cl. (1891). 



Valve elongated, lanceolate, more or less convex and acute, frequently with a wing, or 

 longitudinal band, on one or both sides. Median line straight, on a central, or excentric, keel; 

 its central pores approximate. Axial area indistinct. Central area small, rounded, or transversely 

 dilated. Structure, fine puncta, forming transverse, not radiate, striae, and longitudinal, more or 

 less straight, much finer, strise. Connecting zone not complex. 



Cell-contents. The cell of T. vitrea contains two chro- 

 matophore-plates along the connecting zone, they follow the in- 

 terior of the larger side of the valve; and send some divisions 

 into the keel (Pfitzer: Ban und Entw., p. 93). 



The plates of T. elegans are similar, but they have 

 three deep constrictions nearly dividing them into almost equal 

 patches, the margins of which are deeply indented. T. Lepidop- 

 tera has also two strongly indented or serrated plates along the 

 connecting zone. At the ends of the frustiule are numerous small 

 granules in lively motion. T. conserta has an entirely different 

 arrangement of the cellcontents, so > that it seems questionable 

 whether this species should not be placed in Auricula, the di- 

 visions of the zone being perhaps too delicate to be visible. 

 T. conserta has along the neutral sid,e of the zone a flat plasma- 

 mass including two chromatophore-plates separated by a narrow, 

 oblique fissure. The plasma-mass has a broad sinus at each end. 

 The first known species of this genus is AmpMprora 

 vitred, named 1853 by W. Smith. Other forms have since then 

 been described by Gkbgort, GKevillb and others as Amphiprora, 

 including both forms with sigmoid median line and complex zone, 

 and with straight median line and not complex zone. Rabenhorst 

 1864 proposed (Fl. Eur. Alg. p. 257) for the former the generic name 

 Amphicampa (later on changed by Pfitzer and Grunow to Amplii- 

 t'i'opis) and' retailed the genus Awipfiiprora for the latter. As, 

 however, the first species of Amphiprora {A. alata KtJTZ), so de- 

 scribed as to be distinctly recognized, belongs, to the group with 

 sigmoid median line, it seems to me that that name, rather than 

 Amphicampa, should be retained for this group. In ,1871 Pfitzer 

 created the genus Flagiotropis, and family Plagiotropidce, for forms 

 with straight, excentric, keels lying diagonally in opposite direc- 

 tions, represented by P. laltica Pfitz. which is very probably the same as Amphiprora vitrea W. Sm. 

 For forms with excentric keels lying in parallel directions Grunow 1880 (Van Heurck's Syn. 

 PL XXII bis.) created the genus (or more correctly subgenus of Amphora) Amphoropsis, in which 

 he includes both forms with complex, and not complex, zones. In the year 1891 I (Diatomiste 

 I p. 51) proposed to unite in one genus, Tropidoneis, the forms of Amphiprbra with straight 

 median line, those of Plagiotropis, and of Amphoropsis with non-complex zone. 



Tropidoneis elegans, 600 times magnified. 



