46 TUFTS COLLEGE STUDIES, VOL. IV, No. 7 



15. S. LONGUS Meyen, 1829, p. 774, PI. XLIII, fig. 28; 

 G. M. Smith, 19163, p. 469, PI. XXVIII, fig. 54 ; XXXI, figs. 

 156-158; 5". quadricauda forma sefosus and forma horridus Col- 

 lins, 1909, p. 169. Colony 2-8-celled. cells oblong-cylindric or 

 ovoid, rounded at each end, with one chromatophore and one 

 pyrenoid; a single spine at each pole; cells 8-Ji X 4*5 M 

 spines 2-4 /A long. Wis., G. M. Smith. Europe. 



Occasionally a spine may be wanting of the normal number, 

 but this is exceptional. 



Var. BREVISPINA G. M. Smith, I9i6a, p. 471, PI. XXXI, 

 figs. 151-155. Cells longer and narrower, 9- 1 1 X 3-5 /* ; spines 

 shorter, about 2 /*. Wis., G. M. Smith. 



Var. MINUTUS G. M. Smith, 19163, p. 471, PI. XXXI, figs. 

 147-150. Cells smaller, 6.5-8 X 2-3/1; spines 1.5-2 ft long. 

 Wis., G. M. Smith. 



Var. ELLIPTICUS (W. & G. S. West) G. M. Smith, 19163, 

 p. 472, PI. XXVII, fig. 44; 5. quadricauda var. ellipticus W. 

 & G. S. West, 18953, p. 83, PI. V, fig. 6 ; Collins, 1909, p. 169. 



Var. Naegelii (Brb.) G. M. Smith in litt., nov. comb ; 5". Nae- 

 gelii Brbissou, 1856, p. 158 ; S 1 . caudatus (?) Nageli, 1849, p. 91, 

 PI. V, figs. 2, c & d. Cells larger than in the typical form, 

 18-33 X 7' 11 M. spines 15-30 p. long. Colony usually 8-celled, 

 median cells with usually only one spine each, 3 adjacent cells 

 with spines at the same end, the 3 other with spines at the 

 opposite end. Wis., G. M. Smith. l:itropc. 



16. S. QUADRICAUDA (Turp.) Krcbisson in Brbisson & 

 Godey, 1835, p. 66 ; Collins, 1909. p. 169; G. M. Smith, 19163, 

 p. 472, PI. XXVII, fig. 39; XXXI, figs. 172-175; XXXIII. 

 fig. 176; Achnanthes quadricauda Turpin, 1820, fig. n; 1828, 

 p. 311, PI. XIII, fig. 6. 



Var. QUADRISPINA (Chodat) G. M. Smith, 19163, p. 479, PI. 

 XXVII, fig. 43; XXXI, figs. 167-170; 5. quadrispina Chodat, 

 1913. P- 5 8 figs- 45-52. Cells broad ovoid, 8.5-11 X 3.5-6 /*; 

 spines short. Wis., G. M. Smith. l.uropt. 



Var. PARVUS G. M. Smith, 19163, p. 480, PI. XXXI, figs. 

 162-166. Cells ovoid-cylindric, 5.5-8 X 3 /*; spines 4.5-8 /* 

 long. Wis., G. M. Smith. 



Var. LONGISPINA (Chotlst) G. M. Smith, 19163, p. 480, PI. 

 XXVII, fig. 42; XXXI, figs. 159-161; S.lon K ispina Chodat, 

 1913, p. 60, figs. 53-58. Cells ovoid-cylindric, 8-n X 3.5-5 /*; 

 spines 7.5-14 M long. Wis., G. M. Smith. Europe. 



The spines are 11-14 M long in the European plant, 7.5-9.5 M 

 in the American. 



