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 

 VJAy^SS'H^ size. Penard recognizes six varieties, var. claviformis sometimes 

 •■:^^i^'^i^^^:sr:^^ 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 m- 



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



72 (59) Shell with internal partition or diaphragm 73 



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



tion at the point of constriction. . Pontigidasia Rhumbler. 

 Representative species. . . . Pontigidasia spectahilis Penard 1Q02. 



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 m- 



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



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



diaphragm Cucurhitella Penard. 



Representative species. . . Cucurbitella niespiliformis Penard 1902. 



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



'^Su-H^^ of the neck is a transverse peristome covered with sand grains, resulting 



w^ri^'ij in the rounded aperture being much smaller than the diameter of the 



f^T^.'^'.a, neck itself. Pseudopodia numerous, straight. Found at the bottom of 



)\r^ ponds and lakes. Length from 125 to 140 n. 



<l\\X. Fig. 308. Cucurbitella mespiliformis. X 125. (.\fter 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. 



Bull inula Penard. 

 Representative species Bullinula indica Penard iqc]. 



?k-'?>^7tcr^i?3(^^ Shell brownish, of small siliceous plates, closely cemcnttxl to- 



gether. Superior lip slightly overlapping the inferior lip. 

 '%\ Nuclei numerous. Diameter igo to 200 m. Habitat mosses. 



■^n^'^Rr^^^SrW Fig. 309. Bullinula inJica. X 120. (.■\f tor Penard.) 



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



PI agio pyxis Penard 



79 



