72 DAVENPORT ACADEMY OF SCIENCES. 



Length, 200 microns. (Fig. iii, PI. XIV.) 



This species has been found in a number of localities in this 

 state, lyake Okoboji having furnished some very large specimens. 

 Usually the pharynx is made up of twelve or more rods so united 

 together as to form a cylindrical tube slightly dilated at the 

 exterior end. 



Usually an individual exhibits a variety of colors, which prob- 

 ably result from the breaking down of the algae and other plants 

 of low order upon which it feeds. Found in fresh water. Tri- 

 chocysts are not present in this species. 



NaSSULA RUBENS C. & ly. 



Body elongate, cylindrical, equally rounded at both extremi- 

 ties. Pharynx made up of rod-like teeth forming a cylindrical 

 tube, dilated at the exterior end. 



Nucleus spherical, posterior. Contractile vesicle single. Tri- 

 chocysts very numerous. 



Length, 50-80 microns. (Fig. 112, PI. XIV.) 



This species is much smaller and less abundant than the preced- 

 ing one. The presence of the trichocysts will also readily dis- 

 tinguish it from A^assu/a oronata . 



Found in fresh water a.ssociated with the last named species. 

 Color usually some shade of red. 



CHILODON Ehrenberg. 



Compressed, flexible, ventral surface flattened, with cilia ar- 

 ranged in longitudinal rows. Dorsal surface .somewhat convex, 

 smooth. Anterior extremit}' projecting to the left in a lip-like 

 manner. Oral aperture ventral, leading into an elongated, 

 conical pharynx provided with numerous rods. Nucleus oval, 

 posterior to the center of the body. Contractile vesicles often 

 numerous. 



Chilodon cucullulus Miill. 



Body elongate-oval, rounded posteriorly. Lip-like extension 

 prominent. Oral aperture usually anterior to the middle of the 

 body. A groove leading from the lip-like extension to the mouth. 

 Nucleus oval, near the inner end of the pharynx. Contractile 

 vesicles numerous, scattered. 



Length, 125-200 microns. (Fig. 113, PI. XV.) 



