134 ASCAROIDEA 



male with a few minute bristles. Spicules with bifurcate tips, 

 the anterior fork rudimentary, the posterior somewhat 

 sigmoid and acvite. An accessory piece present, with posterior 

 process. Testis single, anterior, outstretched. Female un- 

 known. Spinneret present. 



Hab. Marine. 



Genotype : I. jiunchdalus Cobb, 1920. 



Cobb, 1920, Contr. Sci. NematoL, ix, 336 and key. 



15. Ypsilon Cobb, 1920. 



Cuticle coarsely striated, with a few bristles in the cervical 

 and caudal regions. Head with four bristles and three 

 minute, indistinct lips, surrounded by three pairs of labial 

 papillae. Pharynx narrow and funnel-shaped, containing a 

 large dorsal tooth, the anterior portion of which is cup- 

 shaped and fixed obliquely on to the main shaft. Oesophagus 

 with cylindroid posterior swelling. Caudal end of male with 

 three minute preanal supplementary organs. Spicules rather 

 slender, appearing as if barbed near their roots. A single 

 slender accessory piece present, with indistinct posterior 

 process. Female undescribed. Caudal glands and spinneret 

 present. 



Hab. Marine. 



Genotype : Y. exile Cobb, 1920. 



Cobb, 1920, Contr. Sci. NematoL, ix, 314 and key. 



16. Monoposthia de Man, 1889. 



Cuticle striated, with bristles. Head with papillae and 

 bristles. Lateral organs small, circular. Pharynx similar to 

 that of Sjyilophora, containing a dorsal tooth. Oesophagus 

 with a posterior bulb. Caudal end of male without preanal 

 or postanal papillae. A single symmetrical spicule present, 

 and no accessory piece, according to de Man.* Testes paired. 

 Female genital tube single, anterior, outstretched. 



Hab. Marine. 



Genotype : M. [Sjyilij^hera] costata (Bastian, 18G5). 



Bastian, 1865, Trans. Linn. Soc. London, xxv, 166; deMan, 

 1889, Mem. Soc. Zool. France, ii, 9. 



17. Thoracostoma Marion, 1870. 



Syn. Iiemi2mlus de Quatrefages, 1846 ; Deontostoma Filip- 

 jev, 1916, Jagerskioldia Filipjev, 1916; Leptosomatides 

 Filipjev, 1918. 



* According to Steiner, a large accessory piece is present in the 

 genotype. The presence of a single spicule, as described by de Man, 

 prevents the inclusion of this genus in Spilopliora, with which it seems 

 to be otherwise in agreement. 



