Rhyacodrilus stephensoni Cernosvitov 1942

16. Rhyacodrilus stephensoni Černosvitov, 1942

(Figure 6)

Rhyacodrilus stephensoni Černosvitov, 1942: 284 –285, Liang & Xie 1992: 196 –197.

Material. 1 spm, whole-mounted in Canada balsam, from ST59, 4 specimens in 10% formalin from ST59 and ST61.

Description. Length 7.8 mm, width in X 0.37 mm, 35 segments. Coelomocytes abundant. Prostomium cylindrical. Pharynx in III–IV. No hairs. Chaetae bifid, distal tooth shorter or equal to proximal, nodulus distal. Chaetae (Fig. 6 B) of anterior segments 3–4 per bundle, posteriorly 2–4 (3) per bundle. Vas deferens (Fig. 6 C, vd) short, 22.5 Μm in diameter, wall 7.5 Μm thin, attached to atrium subapically. Atrium (Fig. 6 C, at) oval-like, ampulla thickly covered with diffuse unicellular prostate gland (Fig. 6 C, pr). Pseudopenes (Fig. 6 C, pe) present, 35 Μm in diameter. Spermathecae (Fig. 6 C, sa) oval-shaped, walls of ampulla 7.5–12.5 Μm thin. Duct (Fig. 6 C, sd) short, 35 Μm long, 47.5 Μm in diameter, 20Μm in its thick wall. Spermathecal chaetae unmodified, 4 per bundle, penial chaetae (Fig. 6 A) straight, bifid, with a very short distal tooth, 3 per bundle.

Remarks. This species was recorded by Stephenson (1909) for the first time as Limnodrilus sp. in Tibet, and then Černosvitov (1942) redescribed it, recognized it as a new species, and transferred it to the genus Rhyacodrilus. This species is also distributed in terrestrial habitats of Tianmu Mountain in Zhejiang Province (Liang & Xie 1997).