COBB: A KEY TO THE GENERA OF FREE-LIVING NEMAS 473 



Nema 9-10 mm.; striae 0; pharyngeat walls heavily cuticularized; amphid small 

 Amphid labial, spiral; phar. large, processes basal; ceph. set. 4; eyes . . (Niidolaimiw Allgen 1929) 

 Amphid 1 head-width back, oval; phar. small; ceph. set. 10; eyes 2 Leptoxomatides Fil 1918 

 Nema under 3 mm.; cephalic setae 4-6 

 Cephalic setae at least 2 head-widths long 



Lip region discoid, set off; odontia 6; amphid small, oval Stephanolaimus Ditlev. 1918 



Lip region not discoid; odontia none; amphid large, circular Cenolaimus Cobb 1933 



Cephalic setae not over 1 head- width long; lip region not discoid; odontia 



Pharynx a wide tube; head strongly conoid; width of nema 6% Tubolaimus Allgen 1929 



Pharynx shallow; head not strongly conoid 



Cutjcle annulated; amphid oval, near lips; lips 3, massive, low Zygonemella Cobb 1920 



Cuticle with fine striae or none; amph. circular, 1 head-width back; lips confluent 



Ribs of pharynx 6, cuticularized, parallel to axis Rhadinema Cobb 1920 



Ribs of pharynx none; pharynx conoid Bognenia Allgen 1932 



Female known (for alternative see preceding page) 

 Ovary 1; amphid not multispire 

 Gonad 9 reflexed; amphid circular or elliptical 

 The ovary posterior; marine 



Spinneret none; cephalic setae 4; tail usually about 40% Rhabdocoma Cobb 1920 



Spinneret present; cephalic setae 0; tail about 3% Nemanema Cobb 1920 



The ovary anterior; cephalic setae present (in Monhystrium sometimes papilloid) 

 Habitat not marine; spinneret present 

 Pharynx deep; onch. small, basal; lips massive, with flaps; vulva 80%; soil (Trischistoma Cobb 1913) 



Pharynx less deep, vestibule definite; onchia 0; in gills of land crabs (Monhystrium Cobb 1920) 



Habitat marine 



Spinneret 0; ceph. set. 10; caudal setae thorn-like; amphid large, center raised (Zanema Cobb 1920) 

 Spinneret pres.; ceph. set. 4, small; thorn-like setae 0; phar. cylind. .(Conolaimella Allgen 1930) 



CSonad 9 outstretched, anterior; usually marine 

 Spinneret none; wings 0; amphid circular; marine 

 Amphid large, with central mound; caudal setae thorn-like; nema 0.9% wide. .(Zanema Cobb 1920) 



Amphid not raised centrally; caudal setae if present not thorn-like 



Labial palps 6; pharynx iquadrate; tail conoid, 4% Crystallonema Cobb 1920 



Labial palps 0; pharynx conoid then spheroid; tail long, filiform. .. .(Diplolaimella Allgen 1929) 

 Spinneret present; marine exc. Monhystrium, and sometimes Monhystera and Theristus 

 Lips 3, each with finger-like odontium; striae coarse; wings 32, fewer towards tail Xyala Cobb 1920 

 Lips without finger-like processes; wings or few 



Mouth cavity large, complex, of several chambers, the first of radial elements; carnivorous 

 Base pharynx unsymmetrical, meeting oesoph. ;middle chamber denticulate Sphaerolaimus Bast. 1865 

 Base pharynx symmetrical.oesoph. surrounding 2 chambers ;dents.O Parasphaerolaimus Ditlev. 1918 

 Mouth cavity smaller, of 1 or 2 chambers, walls relatively simple 



Lips 6, conoid, twice high as broad, with hook-shaped set. ; amph. monospire Dactylaimus Cobb 1920 

 Lips not as high as broad, without hook-shaped setae; mostly Monhysterinae 

 Caudal glands pre-anal, reaching vulva; excret. pore nr. phar.; ceph. set. 4 Conolaimella Allgen 1930 

 Caudal glands post-anal; excret. pore nr. nerve ring, when seen; ceph. set. oft many 



Labial ribs 18, cuticularized, parallel-sided; testes 2 Daptonema Cobb 1920 



(cf. Theristus Bast. 1865) 



Labial ribs absent or (Monhystrium) reduced ;genera resembling Monhystera.exc.Sphaerocephalum 

 Margin of transverse-oval amphidial area not definite, sensory papilla at posterior margin 



Intestine narrow, J body-width; gubernaculum tubular Leptogastrella Cobb 1920 



Intestine wider(?); gubernaculum not tubular(?) Paramonhystera (Steiner) Fil. 1918 



Margin of amphidial area definite, sensory papilla not obvious 



Habitat gills of land crabs; cephalic setae 10, sometimes papilloid Monhystrium Cobb 1920 



Habitat aquatic; marine exc. sometimes Monhystera and Theristus 



Pharynx conoid, then spheroid; striae fine or 0; eyes oft present. .Diplolaimella Allgen 1929 

 Pharynx without spheroid chamber; amphid circular exc. Sphaerocephalum 

 Amphid monospire; neck 5-9%; spinneret wide, plug striated. . .Sphaerocephalum Fil. 1918 

 Amphid circular; neck 10-27%; spinneret without striated plug 



Oesophagus wide in post, half ; spicula hamate distally; gubernaculum Austronema Cobb 1914 

 Oesophagus not wider posteriorly; gubernaculum present 



Setae on head 8-fold; somatic set. oft long. .Steineria (Micol.) Stekhoven & de Coninck 1933 

 Setae on head not 8-fold; long paired somatic setae absent 



Gubernaculum tubular, barbed, apophysis none Fernanda (de Man) Fil. 1918 



Gubernaculum not tubular 



Spicula not much bent; gubernac. apophysate; mostly freshwater. . .Monhystera Bast. 1865 



( = Tachyhodites Bast. 1865) 



Spicula much bent or sickle-shape; gubernac. plate-like, dorsad Theristus Bast. 1865 



( = Allomonhystera Micol. 1923) 

 (cf. Daptonema Cobb 1920) 

 Ovaries 2 



Gonads 9 outstretched; marine (for alternative see next page) 

 Nema 12-16% wide; neck "collared"; amphid spiral; wings many; spinneret present 



Wings over 50; pharynx narrow; spicula 2, equal... Richtersia Steiner 1916 



Wings 16-20, in pairs; pharynx capacious, open; spicula unequal, or but 1 . . (Kichtersiella Kreis 1929) 

 Nema under 3% wide; neck not "collared"; wings if present not numerous 

 Spinneret absent; amphid circular exc. Didelta 



Setae none; amphid ihalf as wide as head Metalaimus Kreis 1928 



Setae present; amphid small exc. Didelta 



Amphid very large, long-oval, on triangular plate; cephalic setae 4 Didelta Cobb 1920 



Amphid small, not on plate; cephalic setae 6 or more 



Pharyngeal bulb distinct; cephalic setae 6, stout, jointed Cytolaimium Cobb 1920 



Pharyngeal bulb none; setae on head 18, small; amph. with faint multispire. . Anticyathux Cobb 1920 

 Spinneret present; cephalic setae present exc. Margonema 

 External amphid multispire 



Male ventral pre-anal supplementary organs papilloid Parasabatieria de Man 1907 



Male supplementary organs none Sabatieria de Rouville 1903 



External amphid not multispire (Linhomoella faintly so) 



