COBB: A KEY TO THE GENERA OF FREE-LIVING NEMAS 461 



External amphid a transverse slit, oft at lip reg.; ceph. set. 0; fresh water or soil (from preceding page) 

 Ovary 1, reflexed; spinneret (Oionchus ?) 

 Spear a closed cutting or pricking organ, tooth-like; vulva 55-60%, ovary anterior 



Spinneret (?) present; spear straight Oionchus Cobb 1913 



Spinneret absent; tip of spear bent dorsad when extruded; amphid elliptical ...Campydora Cobb 1920 

 bpear open at end, a hollow passage, tip not bent; oesophagus dorylaimoid 



Anterior f of oesophagus narrow; cardiac swelling set off by constriction (Doryllium Cobb 1920) 



Anterior |-j of oesophagus narrow; both parts cylindroid 



Narrow part of oesophagus set off behind by constriction Axonchium Cobb 1920 



Narrow part of oesophagus iconfluent with wider posterior part; 9 ' (Dorylaimus Duj. 1845) 



Ovaries 2, reflexed; 9esophagus idorylaimoid 

 Spear a closed cutting or pricking organ, tooth-like 

 The spear long, slender, flexible; cardiac swelling slight, basal, iclavate 



Guide rings for spear absent; spear 30-40% of neck length Trichodorus Cobb 1913 



Guide rings for spear present; spear 20% of neck length Leptonchus Cobb 1920 



Ihe spear shorter, less slender, less flexible; cardiac swelling cylindroid, i-| oesophagus 



Tip of ventral spear oblique, ventrad when extruded; nema 6-10 mm Sectonema Thome 1930 



Tip of submedian spear straight; nema under 4.5 mm Nygolaimus Cobb 1913 



Spear open at end, a hollow passage 

 Pharynx with cup-shaped anterior portion 



Cup-shaped portion with 6 ribs; spear with guiding ring Actinolaimus Cobb 1913 



Cup-shaped portion without ribs ; spear without guide ring ; lip region discoid . . Antholaimus Cobb 1913 

 Pharynx without cup-shaped anterior portion 



Oesophagus with fusiform "bulb" behind spear Dorylaimellus Cobb 1913 



Oesophagus without swelling behind spear 



Lip region discoid, much expanded Discolaimus Cobb 1913 



Lip region usually not discoid, expanded little or not at all 



Labial papillae 0, cephalic 6; circumoral ridge present; vulva 34% Chrysonema Thome 1929 



Labial papillae 6, cephalic 6; circumoral ridge absent Dorylaimus Duj. 1845 



Armature of one or more teeth (odontia or onchia) (for alternative see page 458) 

 Tooth (onchium) 1 (for alternative see page 465) 



Oesophagus plain, i.e. without median or posterior bulb or swelling; amphid occasionally obscure (pg. 463) 

 External amphid not spiral, circular nor elliptical (for alternative see next page) 

 Female not known 



Habitat soil;spinneret 0;phar.i neck-length ;onch.outward-acting;oes.dorylaimoid. .Nanonema Cobb 1905 



(=Cephalonema Cobb 1893) 

 Habitat marine 



Annules coarse, elements tile-like ; amphid crook-shape ; ceph. set. 4 ; nema 0.7 mm . Pselionema Cobb 1933 



(=Steineria Fil. 1922) 

 Annules not coarse; amphid not crook-shape 



Onchium small, a labial prod; cephalic setae 6 Rhinonema Allgen 1927 



Onchium pharyngeal 



Labial set. 6, cephalic 10; onchium dorsal; nema 0.5% wide; amphid transverse Trileptium Cobb 1933 



( = Trilepta Cobb 1920) 



Labial set. 0, cephalic 6; onchium ventral; nema over 4% wide Doryonchvs Kreis 1932 



(cf. Symplocostoma Bast. 1865) 

 Female known 

 Ovary 1 ; habitat not marine 



Median onchium spear-like, dorsal onchium minute, basal Enoplocheilus Kreis 1932 



Median spear-like onchium absent; ovary reflexed; Enoplidae 



Pharynx tubular, depth 10 times width ; tooth basal ; cephalic setae Cryptonchus Cobb 1913 



( = Ditlevsenia Micol. 1925) 

 Pharynx conoid when open, depth not over 3 times width 



Tooth minute, basal, deep-set; denticles 0; spinneret terminal Trischistoma Cobb 1913 



Tooth large, subventral; denticles present; other onchia 2; spinneret ventr&d(Mononchulus Cobb 1918) 

 Ovaries 2 



Gonads 9 outstretched; spinneret present; striae plain; marine Mononcholaimus Kreis 1924 



Gonads 9 reflexed 



Spinneret absent; amphidial opening oval or a transverse slit 

 Base of tooth without "flukes"; cephalic setae 6; onchium large, acute; in soil. .Onchulus Cobb 1920 



Base of tooth anchor-shaped, "flukes" dorsad and ventrad Diphtherophora de Man 1880 



( = Chaolaimus Cobb 1893 

 =Archionchus Cobb 1913) 



Spinneret present, exc. sometimes Eurystominae 

 Habitat not marine; Trilobinae 



Pharynx closed; lips 3 ; onchium minute, basal, deepset Tripyla Bast. 1865 



(=Promononchus Micol. 1923) 



Pharynx open, domed, larger; lips 6; onchia often more than 1 Trilobus Bast. 1865 



Habitat marine 



Striae conspicuous, resolvable into dots or rod-like elements; Chromadoridae 



Amphid at lips, lenticular, oft obscure; cuticle of "basket-work" on neck Euchromadora de Man 1886 



(=Graphonema Cobb 1898) 

 Amphid not at lips, of even width, conspicuous, reaching nearly across head 



Cephalic setae 0; annules of obscure rod-like elements; spicula entire Actinonema Cobb 1920 



Cephalic setae 10; annules on neck of "basket-work" 



Spicula entire; amphid a wide transverse oval Pareuchromadora Stekhoven & Adams 193 



Spicula of 2 sections ; amphid a narrow slit of even width R hips Cobb 1920 



Striae 0, or plain and very fane 



External amph. bent or crook-shaped, plate oval, 1 head-width ;"tooth" minute Diplopeltis Cobb 1905 



( = Dipeltis Cobb 1891 

 =Discophora Villot 1875) 

 External amphid not crook-shaped, plate absent; Enoplidae 



Head with elaborate, ornate calvarium Deontostoma Fil. 1916 



Head without calvarium 

 Pharynx of single chamber; cephalic setae 10 



