Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 59. (Budapest 1967)

Pintér, L.: A revision of the genus Carychium O. F. Müller, 1774, in Hungary (Mollusca, Basommatophora)

Comparing the materials deriving from Telektanya (Upper Tisza) and Szeged (Lower Tisza), the numerical proportion of the two species increases toward the south in favour of C. minimum, whereas in the north, in the vicinity of the mountains, it is C. tridentatum which plays the leading role. With respect to the Danube, collectings had been conducted within a relatively short stretch (Esztergom—Budapest; about 05 km). Though the Danube flows among mountains in northern Hungary, and though Carychium tridentatum thrives abundantly in the tributaries of the river Ipoly which, together with the river Garam, carry their waterborn material also from the Carpathians, the per cent occurrence of C. tridentatum is still so low along the Esztergom—Budapest reach of the Danube that we are at the moment at a loss to account for it. For this very reason it were most gratifying to conduct investigations of the drift, involving the entire length of our streams, to obtain some satisfactory answer concerning the actual origin of the drift species. It is worthy of note, also here, that the origin of Argna species ( = Agardhia), Acicula ( = Acme) perpusilla? (REINH.) (Tisza-drift), and a still unpublished recent Paladilhia species (Esztergom, Danubedrift), is entirely unclarified, though these problems touch heavily on our zoogeographical knowledge. III. Population analysis In the course of separating the two species, it was found that the variability of these taxa is considerably bigger than given in literature. This refers in general to dimensions, or, to be more exact, the ratios of the measurements. To place the matter into a sharper focus, I have selected for our study purposes the biggest material — containing therefore the greatest number of individual aberrations (Garadna valley, Mts. Bükk, 27 Febr., 1951, leg. I. VÁSÁRHELYI). This collecting resulted in 2691 Carychium specimens. Of this rich material, I took a random sample of 200 adult shells and removed with a sharp pin the partion of the penultimate whorl above the aperture to free the parietal lamella, The material was then separated into the two species, to wit: 43 specimens of C. minimum (21.5%) and 157 specimens of C. tridentatum (78.5%). I have then taken 20 specimens of each species and measured, with a hundredth millimeter exactness, the total height, width, and aperture height of all specimens, and then calculated from the values received the proportions of the two ratios (Table 2). Prior to evaluating the results of the investigation, I also submit the data of a population originating from an entirely different region of the country (valley of the Malom brook, Pilismarót, 8 July, 1965, leg. L. PINTÉR). This collection resulted in 252 Carychium specimens. The method of examination was in essence identical with the preceding one (Table 3). Since, in both cases the number of measured specimens were rather small, the data cannot be regarded as completely definitive. There occur presumably smaller and bigger specimens than the examined ones in the populations under discussion, but even this less than wholly satisfactory solution will suffice for our purpose. By separately summing up the numerical values and ratios, and then dividing them with the number of specimens, the means of the two populations were obtained (Table 4).