— 142 



lies in one longitudinal row with the preanal, Avhereas the 

 4-th and 3-rd pairs are replaced towards the medial body- 

 line, the third pair to a greater extent, than the fourth. And 

 lastly, the most posterior papillae — the 1-st and 2-nd pairs — 

 are situated at a considerable distance from the rest, being 

 placed in the region of the attenuated part of the tail not 

 far from the apex of the latter. There are 2 spicula of equal 

 size, reaching 0,238 mm. in length; they are bent ventrally, 

 their width gradually decreasing from the slightly swollen 

 base towards the posterior end. The spicula terminate by a 

 thin round apex. The surface of the spiculum is transversely 

 striated. Dorsally and posteriorly a small gubernaculum ad- 

 joins the spicula, the former being of a much smaller size 

 than the spicula, as in all the species of the genus Oxysoma. 

 It has a characteristic canoe-shape with two tubercles in the 

 anterior part, and with a tuberculated dorsal surface. The 

 length of the gubernaculum reaches 0,085 mm. The opening 

 of the cloaca is situated at a distance of 0,275 — 0,3 mm. from 

 the caudal end. 



The female. At my disposal there was only one speci- 

 men of an immature female 7,5 mm. long, at a maximum 

 width=0,29 mm. in the region of. the genital aperture. The 

 width of the body on the level of the oesophageal bulb rea- 



ched 0,27 mm., in the 



region 



of the anus=0,l36 mm. 



The 

 end, 



a 



length of the oesophagus reached 1,2 mm. The caudal 

 unlike that of the male, was not of the pointed flagellum 

 form of the latter, but had the form of a cone gradually 

 attenuating towards the apex. The anal aperture was situated 

 at a distance of 0,17 mm. from the caudal end. The opening 

 of the vulva was in the posterior half of the body, at 

 distance of 4,2 mm. from the cephalic end. 



The specimen investigated was devoid of eggs. 



X. Genus Isacis Lespes. 



Diagnosis: 



Small Nematodes the mouth-opening of which is limited 

 by 3 flat lips, provided at the edges and from inside by den- 

 ticles. The oesophagus consists of two parts: the cylindrical 

 part, widened in its posterior half, and the bulb with the chi- 

 tinous apparatus. The width of the anterior part of the oeso- 

 phagus is not smaller than that of the bulb. The caudal end 



