NO. 6 CLASSIFICATION OF NEMATODES FILIPJEV 25 



The genus Greeffiella is composed of distinctive setaceous, mostly 

 exceedingly minute species. The head is similar to that of the Des- 

 moscolecidae, but they must form a quite separate family. 



Order MONHYSTERATA 



Under this name are united all the true free-living forms with 

 the straight (not reflexed) ovaries (fig. 51). The amphids are al- 

 ways very distinct and either spiral, horseshoe-shaped, or circular, 

 the last type probably being a reduced spiral. The other morphologi- 

 cal characters are very inconstant. The cuticle is mostly striated, 

 but in some forms smooth. The esophagus is usually without a bulb. 

 The vestibulum is well developed, with a chitinous ring on the bot- 

 tom which serves as a support to the esophagus (fig. 52). This ring 

 is lacking, probably lost, in most of the Linhomoeidae. Very often 

 there is a strengthening of the vestibulum by means of several chiti- 

 nous rods inside its walls (figs. 52, 53) ; these rods are sometimes 

 separated from the walls and can spread forward or sideward when 

 the mouth is open. In spite of the meager morphological character- 

 istics of the group, there are very gradual transitions between its 

 different members, so that it seems to be a very natural one. 



KEY TO FAMILIES OF MONHYSTERATA 



1. (2) Spicules short and strong, distinctly bent to form 



an arch (rarely double), with a strong guber- 

 naculum guiding their ends and armed with two 

 obliquely backward-pointing processes serving 

 to attach muscles Linhomoeidae 



2. (i) Spicules short or long, with a gubernaculum with- 



out backward-pointing processes, or with feebly 



developed ones Monhysteridae 



Subfamilies and Genera of the Family Monhysteridae 



Subfamily Monhysterinae. 



Genera: Paramonhystera Steiner, 1916; Amphimonhystera Allgen, 1929; 

 fPorocoma Cobb, 1920; Penzancia de Man, 1889; Theristus Bastian, 

 1865 (syn. Allomonhystera Micoletzky, 1923); Daptonema Cobb, 1920; 

 Tubolaimus Allgen, 1929; Monhystrium Cobb, 1920; Cobbia de Man, 

 1907; Gonionchus Cobb, 1920; fXyala Cobb, 1920; fRhynchonema 

 Cobb, 1920; Dactylainius Cobb, 1920; Microlaimus de Man, 1880; 

 fBolbolaimns Cobb, 1920; Monhystera Bastian, 1865 (syn. Tachyho- 

 dites Bastian, 1865) ; Diplolaimella Allgen, 1929; Monohystrella Cobb, 

 1918; Scaptrella Cobb, 191 7; Austronema Cobb, 1914; Leptogastrella 

 Cobb, 1920; Omicronema Cobb, 1920; Cylindrolaimus de Man, 1880. 



subfamily Sphaerolaiminae. 



Genera : Crassolaimus Kreis, 1929 ; Sphaerolaimus Bastian, 1865 ; Para- 

 sphaerolaimus Ditlevsen, 1919; fCytolaimium Cobb, 1920. 



