1 0 0 0 OA ドブネズミの下顎臼歯における附加結節について
A supplemental tubercle is often seen on the mesiobuccal part of the lamina on the lower molar of Rattus. We call this the mesiobuccal tubercle to distinguish it from the others. The main aim of this paper is to report on regional differences in its frequency of appearance on the mesiobuccal tubercle and to report on various supplemental tubercles on the lower molar of Rattus norvegicus. I. Regional difference: We have examined the regional difference of frequency of the appearance of the mesiobuccal tubercle in Rattus norvegicus, which were collected in the following four districts; Matsumoto City, Shiga Heights in Nagano Prefecture, Nagoya City and Fukuoka City. The most noticeable difference is found on the second lamina of the second molar. A quite significant difference is that the rate of frequency appearance on the right molar in Nagoya is 66.7%, which is far lower than the others; in Shiga Heights it is 91.7%, in Matsumoto City 95.1%, and in Fukuoka City 92.6%. On the second lamina of the third molar we recognize a regional difference, and especially the rate on the right molar in Nagoya, as well as that of the second lamina of the second molar, is much lower than the rate in the other three districts. II. Various supplemental tubercles which appear on the lower molar are as follows: 1) The supplemental tubercles found on the lingual surface between the first and the second lamina of the second molar. 2) The tubercle found on the distal surface of second lamina of the third molar. This tubercle is homologous to the posterior heel of the first and second molar and seems to be its remnant. 3) The tubercle found on the distobuccal of the first lamina of the first molar.
1 0 0 0 OA 本州八ケ岳のネズミおよび食虫類 : 第1報 亜高山森林帶のネズミおよび食虫類
From April, 1962 to March, 1963, the authors collected small mammals (Rodentia and Insectivora) monthly by snap traps in the subalpine forest zone (Tsugadiversiforia-Abies Mariesii forest zone, alt. 1,300-2,400m) on Mt. Yatsugatake in Honshu. Total number of captured mice and voles was 961 with the following proportional breakdown: Rattus rattus 1, Apodemus speciosus 14, Apodemus argenteus 308, Clethrionomys andersoni 616, Anteliomys smithii 20, Microtus montebelli 2. The number of moles and shrews taken was 231 with the following breakdown: Euroscaptor mizura 1, Urotrichus talpoides hondonis 18, Dymecodon pilirostris 151, and Sorex shinto shinto 61. Rattus rattus and Microtus montebelli were found in this area. Apodemus speciosus and Urotrichus talpoides hondonis were only found in the lower part of this grassy area. On the other hand, Apodemus argenteus, Clethrionomys andersoni, Anteliomys smithii, Dymecodon pilirostris, Sorex shinto shinto were widely found in this forest zone. It was noted that the largest number of Apodemus argenteus appeared in spring, but the peak of Clethrionomys andersoni was seen from autumn to winter (Fig. 2). The average embryo sizes of each species were as follows: Apodemus speciosus 5.7, Apodemus argenteus 3.9, Clethrionomys andersoni 3.3, Anteliomys smithii 3.5, Microtus montebelli 3.0, Urotrichus talpoides hondonis 4.5, Dymecodon pilirostris 3.5, Sorex shinto shinto 3.7. The highest capture rate (number of captured small mammals/no. of set traps) occurred in October and the lowest rate in February. They reflect the effect of the population density and the snow fall, etc.