Dr. Holló Ferenc szerk.: Parasitologia Hungarica 3. (Budapest, 1970)

The close relationship and congenerity of R. exasperatum and R. opisthovitellinum cannot he disputed. As is to he seen from the list of synonyms, the authors had, however, treated these two trematodes as congeners of also other species and in diverse genera until recently till 1966. In his work published in 1966, SKRIABIN elevated the subgenus Rubenstrema

, established by DOLLMJS in the genus Opisthoglyphe

, to a generic rank and assigned the two species to this taxon. SKRIABIN'

s relegation of the two species to a distinct genus appears to be correct in every respect, expecially in view of the following common features: 1. The prepharynx and oesophagus are absent. 2. The uterus does not extend beyond the posterior testis (it projects beyond this latter only insignificantly even in much contracted specimens,or when the testes are weakly developed)

. 3. Related to each other, the testes are situated diagonally (one may shift behind the other only when the posterior end of the body is much extended). 4. The cirrus sac lies in front of the ventral sucker, its base reaching at most the transverse axis of the ventral sucker; it does not project beyond the caudal surface of the ventral sucker. 5. The metraterm is present. The value as a generic feature of the interrupted state of the vitellary glands is, however, doubtful (SKRIABIN, 1966, p.

117). The discontiguity is invariably absent in R. opisthovitellinum

, and might be lacking also in R. exasperatum

, as pointed out by ZARNOWSKI (I960). As regards our R. exasperatum specimens, in four individuals the contiguity of the vitellary glands was interrupted in only one side of the body (in the case of animals