smith: infusoria of Kansas. 161 



recurved. Cuticular surface with longitudinal striations. Macronucleus 

 elongated oval; micronucleus single. Contractile vacuole postero-terminal. 



This is a common parasite in the intestinal tract of frogs. 



Length of type specimen, 175 microns. (Fig. 32, plate XXXIX.) 



Genus Metopus C. & L. 



Body elongated oval, cylindrical, highly elastic and changeable in form. 

 Anterior extremity usually twisted obliquely upward, overlapping the 

 ventral surface. Peristome a long, narrow furrow, extending obliquely 

 from left to right. Pharynx short. Mouth near or posterior to the 

 median line. Body striated and ciliated, longer cilia at the anterior and 

 posterior extremities. Macronucleus cylindrical. Contractile vacuole 

 postero-terminal. 



Metopus sigmoides Mull. 



Body normally elongate, quite changeable in form, about three times 

 as long as broad. Anterior extremity rounded, posterior extremity 

 bluntly pointed. Body striated and covered with cilia, an especially long 

 tuft at the posterior end. Macronucleus oval, centrally located; micro- 

 nucleus single. Contractile vacuole large, terminal. 



Found in pond water. 



Sizes given range from 83 to 260 microns. Size of type specimen, 210 

 microns. (Fig. 29, plate XXXIX.) 



Genus Metopides Quennerstedt. 



Body persistent in foim, ovate or pear-shaped. Anterior region 

 obliquely twisted toward the left over the ventral surface. The groove 

 formed thus is the oral groove and leads to the mouth. Pharynx short. 

 Oral groove strongly ciliated. Cuticular surface entirely covered with fine 

 cilia. Tuft of setae at the posterior end. 



Metopides acuminata Stokes. 



Body pear-shaped. Anterior extremity broad and rounded; tapering 

 posteriorly to a tail-like region. Several long, slender setae at the pos- 

 terior end. Macronucleus spherical, centrally located. Contractile vacuole 

 single, posterior. 



Length of type specimens, 73 microns. (Fig. 31, plate XXXIX.) 



Genus Spirostomum Ehr. 



Body cylindrical or worm-like, greatly elongated, usually rounded an- 

 teriorly and truncated posteriorly. Oral groove extending from the 

 anterior extremity down the ventral surface to the middle of the body or 

 beyond. Adoral cilia bordering the left-hand side of the peristome. 

 Cuticular striated spirally. Macronucleus ovate or moniliform. Anus 

 and contractile vacuole terminal. A tubular canal extending from the 

 contractile vacuole to the anterior part of the body. 



Spirostomum ambiguum Ehr. 



Body from ten to sixteen times as long as broad. Peristome extending 

 to or beyond the middle of the body. Macronucleus moniliform. Contrac- 

 tile vacuole often occupying a third or more of the body, with the canal- 

 like region extending almost to the anterior end. 



