RHABDITIDAE 59 



Two accessory pieces present. Testis apparently single, 

 anterior, outstretched. Female genital tubes paired, opposed, 

 reflexed. Caudal glands and spinneret present. 



Hab. Marine. 



Genotype : Z. nudum Cobb, 1920. 



Cobb, 1920, Contr. Sci. NematoL, ix, 272 and key. 



b. Monhystrium Cobb, 1920. 



Cuticle unstriated, without bristles or lateral alae. Head 

 not distinct, with ten short bristles. Lips three, more or less 

 fused. Lateral organs small, circular. Buccal capsule very 

 much reduced, funnel-shaped. Oesophagus with a pyriform 

 posterior bulb. Caudal end of male without supplementary 

 organs, but with several pairs of postanal papillae. Testis 

 single, anterior, outstretched. Female genital tubes paired, 

 opposed, the posterior branch vestigial. 



Hab. Gill-chambers of Land-crabs. 

 Genotjrpe : M. transitans Cobb, 1920. 



Cobb, 1920, Contr. Sci. NematoL, ix, 284 and key. 



c. Tripylium Cobb, 1920. 



Cuticle smooth, without bristles or alae. Head not distinct, 

 with six papilliform bristles and six labial papillae. Lateral 

 organs incipient spirals. Pharynx wide, thick-walled, form- 

 ing anteriorly three jaw -like inward projections on the inner 

 surfaces of the lips. Oesophagus cylindroid, with a distinct 

 bulb-like swelling posteriorly. Tail of male with three pairs 

 of inconspicuous sub ventral papillae. Spicules slender. A 

 slender accessory piece present. Testis single, reflexed at 

 extreme end. Female genital tube single, anterior, out- 

 stretched. Viviparous. Caudal glands and spinneret present. 



Hab. Gill-chambers of Land-crabs. 



Genotype : T. [Monhystera] carcinicola (Baylis, 1915). 



Baylis, 1915, Ann. Mag. Nat. Hist., (8) xvi, 418; Cobb, 

 1920, Contr. Sci. NematoL, ix, 288 and key. 



There are some discrepancies between the original descrip- 

 tion of " Monhystera " carcinicola and Cobb's account of 

 Tripylium carcinicolum, but the material upon which both 

 were based appears to have come from the same source, and 

 presumably the species is the same. According to the original 

 description, there was evidence that M. carcinicola was a 

 protandrous hermaphrodite. The systematic position of 

 Tripylium is difficult to determine. Its habits and general 

 organization suggest that it should be placed near Monhy- 

 strium, which is here regarded as possibly belonging to the 

 Rhabditidae. The presence of the three jaw-like structures 



