140 ASCAROIDEA 



genus Thalassironns for this form. As regards its morphology, 

 he does not mention any satisfactory distinguishing characters. 



2. Odontophora Biitschli, 1874. 



Cuticle apparently unstriated, with scattered bristles. 

 Head truncate, not distinct, with bristles. Mouth surrounded 

 by tlu'ee triangular tooth-like structiu'es, capable of inversion. 

 Pharynx funnel-shaped, unarmed except for the tooth-like 

 structures mentioned. Oesophagus with a rather pronounced 

 bulb-like posterior swelling. Female genital organs paired, 

 opposed. Male undescribed. 



Hab. Marine. 



Genotype : 0. marina Biitschli, 1874. 



Butschli, 1874, Abh. Senclcenh. Oes., Frankfurt a. M. ix, 3, 285. 



This genus is very imperfectly known, and, apart from the 

 presence of bristles on the body, there appears to be little to 

 distinguish it from Iromis. 



3. Mesonchium Cobb, 1920. 



Syn. Pepsonema Cobb, 1920. 



Cuticle rather finely striated, with some bristles towards 

 the extremities. Head slightly expanded, with indistinct 

 lips. Two crowns each of six labial papillae present, and a 

 single crown of four cephalic bristles. Lateral organs spiral. 

 PharjTix rather narrow, apparently three-sided, containing 

 anteriorly three forwardly-pointing teeth. Oesophagus 

 slightly swollen behind, but without bulb. Caudal end of 

 male with a series of very indistinct nerve-endings. Spicules 

 slender. An accessory piece ( ? two accessory pieces) with 

 slender posterior process present. Testes paired, opposed, 

 outstretched. Female genital tubes paired, opposed, reflexed 

 at their ends. Caudal glands and spinneret present. 



Hab. Marine. 



Genotype : M. poriferum Cobb, 1920. 



Cobb, 1920, Contr. Sci. Nematol., ix, 294 and key. 



Pepsonema is regarded tentatively as a synonym of 

 Mesonchium, the descriptions of the genotyjjes being almost 

 identical. The presence of " one or two minute, onchium- 

 like processes " at the base of the pharynx is mentioned in 

 Pepsonema, but these are not shown in the figure. The 

 spicules are said to be " obscurely retrorsely barbed " in 

 Pepsonema, and this character is not mentioned in Mesonchium. 

 The accessory piece is spoken of in the singular in Mesonchium, 

 and accessory pieces, in the plural, in Pepsonema. 



