182 p. T. CLEVH, SYNOPSIS OF THE NAVICULOID DIATOMS. 



sents C. britannica (the upper valve seems to be some Coscinodisciis). Also C. fraterna A. S. (Atl. 

 CLXXXIX f. 27) seems to be a form of C. britannica. 



2. C. costata Greg. (1855). — More or less elliptical to orbicular. Upper V. with narrow 

 axial area and strong, transverse costge, alternating with double rows of obliquely arranged puncta. 

 Lower V. with the median line reaching nearly to the margin. Axial area narrow. Central area 

 transversely dilated to a fascia narrowed outwardly. Striae radiate, distinctly punctate. 



Var. typica Cl. — L. 0,oi5 to 0,o38; B. 0,oo9 to 0,oi8 mm. Upper V. with linear axial 

 area connected with the margin by strong costse, 5 to 6 in 0,oi mm., alternating with double 

 rows of puncta, forming oblique lines, about 17 in 0,oi mm. Lower V. with indistinct axial area 

 and transversely dilated central area. Striee 15 in 0,oi mm. slightly radiate and distinctly punc- 

 tate; puncta about 16 in 0,oi mm. — G. costata Greg. T. M. S. Ill p. 39 PI. IV f. 10. Vol. V 

 p. 68 PL I f. 27. A. S. Atl. CLXXXIX f 6, 7. V. H. Syn. PL XXX f. 11, 12. Surirella quar- 

 nerensis Grun. Verb. 1862 p. 456 PL IX f. 10 (1862). Rhaphoneis seutelloides Grun. Verb. 1862 

 p. 383 PL IV f. 34. 



Marine: Arctic America! Greenland! Davis Straits! Canada! Spitsbergen! Finmark! Behring 

 Island! North Sea! Mediterranean Sea! Adriatic! Auckland (Grun.). 



Var. hexagona Grun. (1881). — V. broad, linear, with cuneate ends. L. 0,oi.5 to 0,02; 

 B. 0,009 mm. Costse of the upper valve 8 in 0,oi mm. — C. costata var. hex. Grun. V. H. Syn. 

 PL XXX f. 15 to 17. 



Marine? 



Var. pacifica Grun. (1867). — Elliptical. L. 0,027 to 0,o5; B. 0,oi5 to 0,035 mm. Upper 

 V. with linear axial area and strong costse, 5 to 6 in 0,oi mm., radiate at the ends, crossed on 

 both sides of the area by a longitudinal line and alternating with double rows of puncta, 12 to 

 16 in 0,01 mm. Lower V. with transversely dilated central area connected with a marginal blank 

 band, crossing the faint and iinely punctate striae, about 8 in 0,oi mm. — C. pacif. Grun. Novara 

 p. 11 PL I f. 10. V. H. Syn. PL XXX f. 13, 14. C. Imperatrix A. S. Atl. CLXXXIX f. 11 to 

 15 (1894). C. JaniscUi A. S. Atl. 1. c. f. 33? G. exoptata A. S. Atl. CXC f. 31? G. prcestans 

 A. S. Atl. CXC f. 32? 



Marine: Ceylon! Magellans Straits! Chile (Grun.), Oamaru, fossil! 



Var. kerguelensis Pet. (1888). — Elliptical to orbicular. L. 0,055 to 0,i ; B. 0,05 to 0,085 

 mm. Upper V. with narrow, linear axial area. Costse 4 to 6 in 0,oi mm. alternating with double 

 rows of puncta, about 10 in 0,oi mm., forming oblique lines. Lower V. with the median line 

 ending near the margin. Axial area very narrow. Central area a transverse, outwardly narrowed 

 fascia. Striae 4 in 01 mm. composed of double rows of puncta, 10 to 12 in 0,oi mm. and crossed 

 near the margin by a narrow blank band. — G. kerguelensis Pet. D. de Cape Horn p. 116 PL X 

 f. 5. A. S. Atl. CLXXXIX f. 9. C. Eegina Johns. M. J. VIII p. 13 PL If. 12? G. extravagans 

 Jan. a. S. Atl. CLXXXIX f. 28 to 32. 



Marine: Kerguelens Land! Magellans Straits! 



The var. kerguelensis cannot in my opinion be separated as a distinct species from G. costata, 

 however different it may look at the iirst glance. The important characteristics are the same for 

 both, and the differences consist only in size, number of costae and striae. The difference in size 

 is enormous, G. kerguelensis being gigantic compared to G. costata. 



Heteroneis Cl. N. G. 



Frustule without rim. Valves very dissimilar, in outline elliptical or elliptic-lanceolate. 

 Upper valve striate or costate, with a large area. Lower valve either without, with uniting 

 axial and central, or without axial and with quadrate central, area. 



