180 ILLINOIS BIOLOGICAL MONOGRAPHS [418 



6( 5) Spore regularly ovoidal ; polar capsules short pynf onn, opening on opposite sides ; 

 sutural diameter 9/u, breadth \6y.. Trophozoite pyriform without any recog- 

 nizable pseudopodium 



Leptotheca fusiformis Davis 1917 (63) 



7( 2) Average sutural diameter of spore equal to or larger than 10/* 8 



8(13) Shell-valves symmetrically built; sutural ridge straight 9 



9(10) Posterior margin of spore concave in front view; sutural diameter lO/iz, breadth 

 18 to 20/*; each spore formed independently 



Leptotheca informis Auerbach 1910 (63) 



10( 9) Spore regularly ovoidal 11 



11(12) Trophozoite extremely polymorphous. Spore: sutural diameter 10 to 12/«, 

 breadth 18 to 20/1 



Leptotheca polymorpha Th61ohan 1895 (61) 



12(11) Typical form of trophozoite elongated; anterior end depressed surrounded by 

 short often branched pseudopodia. Spore: sutural diameter 12 to 15/i, 

 breadth 18 to 20/t 



Leptotheca elongata Thdohan 1895 (60) 



13( 8) Shell-valves asymmetrically built; sutural ridge sinuous; sutural diameter 9 to 

 lO/i, breadth 16 to 18/*. Trophozoite rounded; movements slow 



Leptotheca lobosa Davis 1917 (64) 



14( 1) Sutural diameter equal to or less than half of greatest breadth 15 



15(18) Average sutural diameter smaller than 10/« 16 



16(17) Spore arch-shaped in front view; polar capsules pyriform; sutural diameter 3 to 

 4/*, breadth 8 to lO/i 



Leptotheca parva Thelohan 1895 (61) 



17(16) Spore cylindrical; sutural diameter 4.5/t, breadth 9/» 



Leptotheca glomerosa Davis 1917 (65) 



18(15) Average sutural diameter greater than 10/* 19 



19(20) Posterior margin of spore slightly concave in front view ; anterior end attenuated ; 

 polar capsules pyriform; sutural diameter 13/*, breadth 26/t. Trophozoite 

 rounded; with active amoeboid movements 



Leptotheca macrospora Auerbach 1909 (62) 



20(19) Posterior margin of spore more or less flattened; anterior end smoothly rounded; 

 polar capsules rounded; sutural diameter 11/*, breadth 22 /t. Trophozoite 

 elongated; pseudopodia often anastomose 



Leptotheca scissura Davis 1917 (64) 



Incompletely described species 



Leptotheca renicola Thelohan 1895 (61) 



Leptotheca hepseti Thelohan 1895 (62) 



Leptotheca perlata Gurley 1894 (62) 



Leptotheca sp. Awerinzew 1908 (62) 



Genus CERATOMYXA Thelohan 1892 



1(52) Spore constant in form and size 2 



2(21) Sutural diameter equal to or less than one-eighth of total breadth 3 



3(10) Sutural diameter not less than one-tenth of total breadth 4 



4( 9) Pseudopodia of vegetative form located at rounded end 5 



5( 6) Pseudopodia long filiform; with slow whiplash-like movements toward pointed 

 extremity. Spore: sutural diameter 12/t, breadth 118/* 



Ceratomyxa flagelUfera Davis 1917 (77) 



Numbers enclosed in parentheses refer to the page of the article on which is found the description of the species 

 named. ^ 



