79., Materials to the knowledge of the Cenozoic non-Marine Mollusca of North China (Part 1)

Abstract

The fossil gastropods dealt with in the present paper were collected by Dr., Tetsugoro WAKIMIZU from the loess at Tsingsing and the terrace deposit (the so-called "redeposited loess") at Shihkiachwang, both in Hopei Province., The material from Tsingsing comprises only three species as follows: Bradybaena (Manchurohelix) lavrushini (COCKERELL) (2 specimens) Cathaica fasciola (DRAPARNAUD) (4 specimens) Cathaica pulveratrix (von MARTENS) (2 specimens) Bradybaena lavrushini still lives in this district and the two species of Cathaica are most common snails in North China, both fossil and living., The state of preservation of the fossils is very excellent., The collection from Shihkiachwang contains three species of fresh-water gastropods and two of land snails, as listed below : Lymnaea (Galba) pervia von MARTENs (about 10 specimens) Lymnaea (Radix) plicatula BENSON (3 specimens) Anisus (Gyraulus) sp., (1 specimen) Opeas pyrgula SCHMACKER and BOETTGER (7 specimens) Metodontia yantaiensis (CROSSE and DEBEAUX) (6 specimens) All the species are now widely distributing throhghout North China., Most of the specimens before hand are not well preserved., The detailed synonymy, the dimensions the recent distribution and the fossil occurrence of each species are shown in the foregoing pages., Further, a tentative correlation table of the Cenozoic formations in North China and Manchuria is given in page 92, detailed discussion of which, however, will be reserved for another occasion., The results of the taxonomic studies are summarised as follows : 1) Limnaea (Gulnaria) shantungensis JONES and PRESTON (1904), Limnaea kingi PING and YEN (1933), Limnaea truncatula tenua PING and YEN (1933) and Galba laticallosiformis YEN (1937) are all synonyms of Lymnaea (Galba) pervia von MARTENS., The specimens of Lymnaea from South Ordos being referred to Galba truncatula (MULLER) by YEN (1937) are also identifiable with pervia, while Limnaea exigua PING and YEN (1933) described from Aksu evidently belongs to Lymnaea (Galba) truncatula (MULLER)., 2) Limnaeus chefouensis CLESSIN (1886), Limnaeus mollendorffianus CLESSIN (1886), Limnaea mars JONES and PRESTON (1904) and Limnaea whartoni JONES and PRESTON (1904) may be synonymous with Lymnaea (Radix) plicatula BENSON., Further, the specimens from Tai-hu being assigned to Limnaea clessini NEUMAYER by ANNANDALE (1918) undoubtedly belong to plicatula, and the shells referred to clessini by YEN in his recent paper (1937) on gastropods of North China seem more closely related to plicatula than to NEUMAYER's species., In the Ryukyu Islands, there is inhabiting a form of Lymnaea which can hardly be distinguished from plicatula., Many Japanese authors have referred it to Limnaea minor BENSON, but this identification does not seem reliable., In his description of minor, BENSON has given neither its illustration nor dimensions and has stated that it strongly resembles Lymnaea (Galba) truncatula (MULLER)., This species has never been reported from the Asiatic Continent, since it was first described from the Chusan Islands., 3) Opeas fragilis PING (1929), a fossil species from the Choukoutien formation, is nothing but a synonym of Opeas pyrgula SCHMACKER and BOETTGER., 4) A detailed description of Bradybaena lavrushini (COCKERELL) is given by Isao TAKI in a paper entitled "Mollusca of Jehol" (Report of the First Scientific Expedition to Manchoukuo, section 5, division 1, part 1, article 4) which will be published in the near future., A new subgenus, Manchurohelix, is proposed by him for this species basing upon the shell characters, and the composition of the genital system., 5) Cathaica transitans von MOLLENDORFF may be understood as an extremity of the individual variation, or at most as a subspecies, of Cathaica fasciola (DRAPARNAUD). [the rest omitted]