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



16. G. constrictuitt Ehb. (1830). — V. clavate, gibbous in the middle, with broad, rounded- 

 trmicate apex and narrower basis. L. 0,04 to 0,06; B. 0,oi mm. Axial area narrow linear; central 

 area narrow, star-like. Stigma distinct, unilateral. Striae 10 to 12 in 0,oi mm., slightly radiate, 

 in the middle alternately longer and shorter, coarsely punctate. — Ehb. Abh. 1830 W. Sm. 

 B. D. PI. XXVIII f. 236. V. H. Syn. p. 123 PI. XXIII f. 6. G. pohlimforme KtJTZ. Dec. N:o 25 

 (1833). G. subramosum Kutz. IJec. N:o 152 (1836) fide Lagst. G. constr. var. subcapitata GrRUN. 

 V. H. Syn. f. 5. 



Fresh water: Sweden! England! Belgium (V. H.), Switzerland! Jenissey! Australian Alps! 

 North Australia! Tasmania! Illinois! 



Var. capitata Ehb. (1838). — V. very slightly or not constricted, clavate with broad apex. 

 - G. capitatum Ehb. Inf. PI. XVIII f. 2. W. Sm. B. D. PL XXVIII f. 237. V. H. Syn. p. 123 

 PL XXIII f. 7. Petit Lac des Vosges f. 3. G. turgidum Ehb. M. G. PL II: 2 f. 40. V. H. Syn. 

 PL XXIII f. 11. G. italicum Kutz. Bac. p. 85 PL XXX f. 75. V. H. Syn. PL XXIII f. 8. 

 G. clavatum Ehb. Inf. p. 218 PL XVIII f. 6. V. H. Syn. PL XXIII f. 9. 



Fresh water: Sweden! Gulf of Bothnia! Finland! England! Belgium (V. H.), France! New 

 Zealand! Canada, foss.! New York, foss. ! Argentina! Ecuador! 



G. constrictum is a very common species with very variable outline. Typical specimens are 

 strongly biconstricted, but all possible intermediate forms exist to the quite unconstricted var. ca- 

 pitata. The characteristic present in all these forms is the stellate central area arising from the 

 median striae being alternately longer and shorter. 



17. G. geminatum Lyngb. (1819). — V. strongly biconstricted, with broad, subtruncate 

 apex and less broad, obtusely truncate basis. L. 0,i to 0,12; B. 0,o3 to 0,04 mm. Axial area 

 narrow, linear; central area rounded, stellate at its margin, with one or, usually, several, stigmas, 

 disposed in a longitudinal row on one side of the central nodule. Striae 10 in 0,oi mm. radiate 

 at the ends, in the middle alternately longer and shorter, coarsely punctate; puncta 12 in 0,oi 

 mm. — Vorticella pyraria Mull. 1773 (fide Ktitz.). EcMnella geminata Lyngb. Tent. Hydroph. 

 p. 210. Gomph. gem. Ag. Syst. p. 12 (1824). W. Sm. B. D. PL XXVII f. 235. 



Fresh water on stones in rivulets and lakes: Spitsbergen, Beeren Eiland (Lagst.), Faroar 

 (Lyngb.), Scotland! Ireland (Ktitz.), Sweden! Finland! France, Cantal (Herib.), Spain, Aragonia 

 (Mouzon), Switzerland (Brun), Vancouver Island! 



Var. sibirica Geun. (1878). — V. slightly or indistinctly biconstricted, with broad end. L. 

 0,08 to 0,09; B. 0,035 mm. Stigma single. Striae 9 to 10 in 0,oi mm. — Grun. Gasp. See Alg. p. 11. 

 G. gem. var. hybrida Grun. V. H. Syn. PL XXIII f. 4. Franz Josephs Land D. p. 97| (45) PL I f. 11. 



Fresh water: Ochotsk (Grun.), Franz Josephs Land (Grun.), Jenissey! 



Var. curvirostra Temp, and Brun (1889). — V. deeply biconstricted, arcuate. L. 0,012 to 

 0,145 mm. Central area with a single stigma. Striae 6 to 8 in 0,oi mm. — G. curvirostrum Temp. 

 and Brun D. f. du Japon p. 38 PL IX f. 4. 



Fresh water: Yedo foss. (Temp, and Brun). 



G. geminatum, the largest of all species of this genus, is a northern and alpine form, being 

 very common in Scotland, Sweden and Finland, where it occurs attached to stones by strong 

 stalks. Between the strongly biconstricted type and the broadly clavate var. sibirica all kinds of 

 intermediate forms exist. The var. curvirostra is a cymbelloid form, such as occurs also among 

 the forms of other species. 



18. G. ventricosum Greg. (1856). — V. lanceolate-clavate. with broad, obtuse apex and 

 narrower basis. L. 0,035 to 0,055; B. O.oi mm. Axial area linear lanceolate. Central area 

 rounded, with one distinct stigma. Striae 11 to 13 in 0,oi mm., radiate, finely punctate; puncta 

 about 24 in 0,oi mm. — Greg. M. J. IV PL I f. 40. V. H. Syn. PL XXV f. 13. Cl. M. D. N:o 93. 



Fresh water: Scotland (Greg.). Norway! Sweden! Finland! Jenissey! Kamtschatka! "Waltham, 

 Massachusetts! 



