14 DAVENPORT ACADEMY OF SCIENCES. 



This Species is also a rare one and seldom is it found in an 

 active condition. Fig. 14 represents the most common variety 

 found in this state, having a rounded fundus and broad, flaring 

 neck. Fig. 15 illustrates a curious variety found in Johnson 

 county, having an exceedingly long neck terminating in a flaring 

 rim. Between the distal end of the neck and the body proper 

 were two other annular ridges, giving the appearance of a once 

 completed shell with later additions. 



Found in pond water among diatoms and other plants of low 

 order. 



DiFFLUGiA CONSTRICTA Leidy. 



Shell oval in form with the anterior border obliquely truncate, 

 composed of sand grains and other foreign materials. Fundus 

 rounded, with or without spines. 



Length, 100 microns. (Fig. 17, PI. III.) 



Rarely has this species been found in the waters of this state. 

 Fig. 17, PI. Ill, illustrates a typical form of the species as observed 

 in Johnson county. These specimens were small individuals, as 

 Leidy reports that only the larger varieties bear spines. Norte of 

 those which I have observed possessed spines. In disposition 

 the organism is shy, seldom extending p.seudopodia. 



The size of the shell, according to Leidy, may range from about 

 90 to 200 microns in length. Those observed in this state were 

 approximately 100 microns in length. 



DiFFLUGIA ACUMINATA Ehr. 



Shell usuall}^ composed of sand crystals, oblong-oval in shape, 

 the fundus prolonged into an elongated process more or less 

 acuminate; no spines. 



This species has a wide distribution and has been found in 

 almost every locality of the state where I have made an examin- 

 ation of the waters. 



Figure 13, Plate II, represents a typical form of Difflugia acu- 

 minata, although great variations may occur in the size and shape 

 of the shells. The posterior acuminate process, although a char- 

 acteristic of this species, [^may be possessed by other species. I 

 have observed it in Difflugia'jirccolata , and an approach to it in 

 Difflugia cratera. Intergrading forms are not uncommon, having 

 characters of more than one species. 



