186 I'. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



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

 truncate apex and narrower basi.s. L. 0,04 to 0,o6; B. 0,oi mm. Axial area narrow linear; central 

 area narrow, star-like. Stigma distinet, unilateral. StrijK K) to 12 in 0,ui mm., sliglitly radiate, 

 in the middle alternately longer and shorter, coar.sely punutate. — Ehb. Abh. 1830 W. Sm. 

 B. D. Pl. XXVIII f. 236. V. H. Syn. p. 123 Pl. XXIII f. 6. G. i)o}iUceforme Kutz. Dec. N:o 25 

 (1833). G. suhramosum KiJTZ. Dec. N:o 152 (1836) fide Lägst. G. constr. var. suhcapitata GRf.\. 

 V. H Syn. f. 5. 



Presh water: Sweden! England! Belgium (V. H.), Switzerland! Jenissey! Aiistralian Alps! 

 North Anstralia! Tasmania! Illinois! 



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

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

 Pl. XXm f. 7. Petit Lac des Vosges f. 3. G. tnrgidum Ehb. M. Gr. 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. clavatmn 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 strife being alternately longer and shorter. 



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

 apex and less broad, obtusely truncate basis. L. 0,i to 0,12; B. 0,03 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. Strise 10 in 0,oi mm. radiate 

 at the ends, in the middle alternately longer and shorter, coari^ety punctate; puncta 12 in 0,(ii 

 mm. — Vorticella pxjraria Mull. 1773 (fide Kiltz.). EchincUa 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 (Lägst.), Färöar 

 (Lyngb.), Scotland! Ireland (Kiitz.), Sweden! Finland! France, Cantal (Hérib.), Spain, Aragonia 

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



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

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

 G. gem. var. hyhrida 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. cnrvirostra Temp. and Brun (1889). — V. deeply biconstricted, arc.uate. L. 0,012 to 

 0,14 5 mm. Central area with a single stigma. Striaj 6 to 8 in 0,oi mm. — G. currirostruni Temv. 

 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 b}- strong 

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

 intermediate forms exist. The var. cnrvirostra is a cymbelloid form, sueh 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 distinet stigma. Striaj 11 to 13 in 0,oi mm., radiate, fiiielj- punctate; puncta 

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



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

 Massachusetts ! 



