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



14. A. glgantea Grun. (1860). — Frustule strongly constricted. L. 0,i2 to 0,i6 mm. Keel 

 with a hyaline margin, broader towards the ends. Junction-line uniformly arcuate, not sinuose. 

 Keel with puncta forming obliquely decussating rows, 13 to 15 in 0,oi mm. Striae of the valve 

 curved, divergent from the central nodule, about 14 in 0,oi mm., not decussating. Median line 

 strongly sigmoid. Connecting zone with numerous longitudinal divisions. — GtRUN. Verh. 1860 

 p. 568 PI. VI f. 12 (bad!). A. D. p. 63. — PI. I f, 6. A. gig. var. kerguelensis Grun. A. D. 

 p. 63 (1880). 



Marine: Mediterranean Sea! Adriatic! Macassar Straits! Kerguelens Land! 



This is a very large diatom, with somewhat thin silicious membrane. When dry the keel 

 under a low power is yellow, and the valve hyaline. 



Var. tahitensis Grun. (1880). — Frustule membranaceous. L. 0,o6 (to 0,095); B. 0,04 mm. 

 Keel strongly sigmoid. Striae 18 to 22 in 0,oi mm. — A. D. p. 63. 



Marine: China! Japati! Tahiti (Grun.). 



Var. (Bquatorialis Cl. (1873). — L. 0,io to 0,i5 mm. Striae 9 to 11 in 0,oi mm. — Amphi- 

 campa cequatorialis Cl. D. Sea of Java p. 12 PI. Ill f. 17. Amphipr. balearica Grun. A. D. 

 p. 63 (1880). 



Marine: Balearic Islands! Adriatic! Java! 



Var. sulcata O'Meara (1871). — L. 0,09 to 0,i4 mm. Striae 12 to 13 in 0,oi mm., on the 

 connecting zone 20 in 0,oi mm. — A. sulcata O'M. M. J. (N. S.) Vol. XI p. 22 PL III f. 3. 

 A. pelagica Brun. D. Esp. n. p. 8 PL XXII f. 3, 4 (1891). 



Marine: Le Croisic! Balearic Islands! Seychelles! Cape Good Hope! Sumatra! Jamaica 

 (Grove Coll.)! 



Var. decussata Grun. (1880). — L. 0,0 6 3 to 0,06 5 mm. Keel slightly sigmoid. Striae 21 to 24 

 in 0,01 mm. — A. decussata Grun. A. D. p. 63. V. H. Syn. PL XXII f. 13. 



Miarine: Courselles (Grun.). Hungary, fossil (Pant.). 



Var. septentrionalis Griw. (1880). — L. 0,o76 to 0,i8 mm. Striae 20 to 23 in 0,oi mm. — 

 A. sept. Grun. A. D. p. 63. 



Marine: Finmark! Cape "Wankarema! 



Auricula Caste. (1873). 



Valve more or less reniform or cymbiform, elevated into an asymmetrical, arcuate, 

 but not sigmoid, keel. Median line not sigmoid, more or less biarcuate, with approximate 

 central pores. Structure: transverse striae, or more or less curved, irregular lines. Frustule 

 usually globose, with complex connecting zone. Keels of both valves turned in the same 

 direction. 



The first known species was the diatom, described 1857 by Gregory as Amphiprora complexa. 

 The genus Auricula was founded 1873 by Castracane (Atti del accad. pont. dei Lincei XXVI p. 

 406) for A. AmpJiitritis, which is evidently nearly akin to^. complexa. In Van Heurcks Synopsis 

 (PL XXII bis f 9, 10) Grunow has proposed the name Amphoropsis for two forms, of which one, 

 A. decipiens, is related to Auricula, and the other, A. recta, is by me considered as belonging to 

 Tropidoneis. As A. decipiens in my opinion cannot be separated from Auricula, I propose to 

 reserve the name Amphoropsis for a section of Tropidoneis. 



The valve of Auricula is keeled as in Amphiprora, but the keel is not sigmoid. In 

 some species, which approach to Amphiprora, the keel is separated from the lower part of the 

 valve by a line of junction. In other forms there is a gradual slope from the median line to 

 the margin. 



