AMOEBOID PROTOZOA (SARCODINA) 



225 



70 (71) Pyriform, with posterior border usually rounded. 



Difflugia pyriformis Perty 1852. 



This very common species is exceedingly variable in form and 

 size. Penard recognizes six varieties, var. claviformis sometimes 

 reaching a length of 450 M - The posterior border is usually 

 rounded but some forms may approach the acuminate type. 

 FIG. 305. Difflugia pyriformis. Found everywhere in the ooze of ponds and lakes. 

 X 60. (After Leidy. ) 



71 (70) Elongate, cylindrical, with posterior border acuminate. 



Difflugia acuminata Ehrenberg 1830. 

 Shell cylindrical, the slightly broader posterior extremity taper- 

 ing to an acute point ending in a knob-like process. Very widely 

 distributed with other species of the genus. Large forms may reach 

 a length of 275 n. 



FIG. 306. Difflugia acuminata. X 125. (After Leidy.) 



Shell with internal partition or diaphragm. ......... 73 



73 (74) Shell with deeply constricted neck and transverse, perforated parti- 

 tion at the point of constriction. . Pontigulasia Rhumbler. 

 Representative species. . . . Pontigulasia spectabilis Penard 1902. 



72 (59) 



Resembling Difflugia Pyriformis in appearance, except for the 

 deeply constricted neck. The internal partition has one round 

 opening and one or two other apertures, the latter being closed by 

 transparent opercula. Pseudopodia few, long, and move rapidly. 

 Found with species of Difflugia. Average length 150 ft. 



FIG. 307. Pontigulasia spectabilis. x 100. (After Penard.) 



74 (73) Shell with a short neck; aperture partially closed by a transverse 



diaphragm Cucurbitella Penard. 



Representative species. . . Cucurbitella mespiliformis Penard 1002. 



The neck is quadrilobate with an undulating margin. On the inside 

 of the neck is a transverse peristome covered with sand grains, resulting 

 in the rounded aperture being much smaller than the diameter of the 

 neck itself. Pseudopodia numerous, straight. Found at the bottom of 

 ponds and lakes. Length from 125 to 140 /*. 



FIG. 308. Cucurbitella mespiliformis. X 125. (After Penard.) 



75 (58) Shell primarily of formed elements 76 



76 (81) Shell not compressed, of small siliceous particles, aperture lunate 



with inferior and superior lips 77 



77 (78) Shell hemispherical or elliptical, superior lip with pores. Large size. 



Buttinula Penard. 

 Representative species Bullinula indica Penard 1907. 



Shell brownish, of small siliceous plates, closely cemented to- 

 gether. Superior lip slightly overlapping the inferior lip. 

 Nuclei numerous. Diameter 190 to 200 n. Habitat mosses. 



FIG. 309. Bullinula indica. X 120. (After Penard.) 



78 (77) Shell hemispherical, superior lip without pores. Small size. 



Plagiopyxis Penard 



79 



