Dr. Kassai Tibor - Dr. Murai Éva szerk.: Parasitologia Hungarica 7. (Budapest, 1974)
in this respect. However the two species in question can not be considered identical, because of a very important feature neglected in the course of the investigations referred to. The most important and practically the only characteristic to distinguish P. simillimum from P. spiculigerum is the size of the pharynx and the ratio of the measurements of the pharynx to those of the oral sucker. The pharynx of P. simillimum is considerably larger than the oral sucker, whereas the measurements of these two organs of P. spiculigerum shows is inverse ratio. LINSTOW did not discuss the pharynx or its measurements in his description, and did not give a figure of the new species described by him. On the other hand LÜHE' s description (1909), following LINSTOW's states that the pharynx is "significantly smaller than the oral sucker". It is not clear from LÜHE' s work whether he saw LINSTOW's type specimens or simply described the species on the basis of LINSTOW's paper. This latter seems more likely, therefore he gave no redescription. After LÜKE, WERTEJUK + considered the pharynx of LINSTOW's P .oligoon smaller than its oral sucker, and thus synonymized P.spiculigerum , described later by MÜHLING. The size of the pharynx is the only differentiating feature of the two Psilotrema species described by MÜHLING. Accordingly, the synonymization by WERTEJUK is unfounded, since the relevant feature concerning P .oligoon is lacking from the original description, and thus LINSTOW's description fits the descriptions of both Psilotrema species given by MÜHLING, and vice versa. MÜHLING noted in his paper that he sent the type-specimen of P. spiculigerum to LINSTOW, who, after examining it,assured him that the specimen was not identical with P. oli goon . On the basis of the above considerations P. oligoon (Linstow, 1887), should be regarded as a "species inquirenda", whereas P_. simillimum and P. spiculigerum (Mühling, 1898) are two distinct and valid species. + WERTEJUK does not refer to LINSTOW's original description, and does not list LINSTOW's paper in the references.
