NO. 6 CLASSIFICATION OF NEMATODES FILIPJEV I3 



Oncholaiminae, but the taxonomic relations of these nematodes are 

 not quite certain. 



The Eurystominae (fig. 13) are related to the Oncholaiminae but 

 distinct enough to be separated. They do not have lips around the 

 mouth except in Ditlevsenella. In typical genera the single onchium 

 is protrusible. Very characteristic is the spicular apparatus (fig. 14) 

 with the thin and strongly curved spicules and two distinctive pre- 

 anal organs. In the genus Bolbella the esophagus is divided pos- 

 teriorly into eight bulbi, an exceptional structure, not only among 

 the bulbless Enoplata, but also among all other Nematoda ; its mouth 

 capsule and the spicular apparatus are quite typical. 



The Enchelidiinae are similar to the Eurystominae as regards 

 the mouth capsule with its protrusible onchium (fig. 15). The long 

 spicules suggest a possible relation to the Phanodermatinae. Oddly 

 enough there exists a polybulbous genus, Polygastrophora, with all 

 the peculiarities of the subfamily, parallel to Bolbella of the 

 Eurystominae. Very interesting is the disappearance of the mouth 

 capsule in the males of certain genera. De Man (1922c) described 

 a form belonging to Cafalaimus, in which the male lacks the mouth 

 capsule although the female has a typical one. Such males were 

 known long ago under the name of Enchelidium (fig. 16). In de- 

 scribing the Black Sea species, I called attention to the strange fact 

 that only the males of this genus were described by the numerous 

 authors studying them, but only De Man's discovery provided an 

 explanation of the problem. In the head, which is always very 

 narrow, there are two cuticular lenses very similar to those of 

 Symplocostoma; the esophageal tube anterior to them is very narrow, 

 as if really reduced. The pigment spot is in the vicinity of the lens. 

 The cuticular lens, as one concludes from comparison with some 

 species of Symplocostoma, represents nothing other than the bottom 

 plate of the mouth capsule. Two interesting points are to be noted 

 here: first, that of the change of functions; second, an example of an 

 organ so highly rated by systematists, disappearing in the same 

 species, in the same individual even, during its molts. 



Subfamilies and Genera of the Family Trilobidae 

 Subfamily Trilobinae. 



Genera: Tripyla Bastian, 1865 (syn. Promononclms Micoletzky, 1923; sg. 

 Trischistoma Cobb, 1913) ; Diplohystera Cillis, 1917; Trilobus Bastian, 

 1865 (syn. Paratrilohus Micoletzky, 1922) ; Cryptonchus Cobb, 1913 

 (syn. Ditlevsenia Micoletzky, 1925); Gymnolaimus Cobb, 1913; 

 Udonchus Cobb, 1913; Onchuliis Cobb, 1920; Prismatolaimus de Man, 

 1880. 



