Abstract: Bedford's vole (Proedromys bedfordi) is a very rare rodent distributed in western Sichuan and southern Gansu province, People's Republic of China. At present, only three specimens have been collected. The taxonomic status of Bedford's vole has elicited controversy. Many zoologists put this species in Microtus. During a baseline survey of the Jiuzhaigou National Nature Reserve in 2003, 16 specimens of Bedford’s vole were collected. The skull, teeth, glans penis were studied. Results show that the third lower and upper molar of adults differ from those of juvenile voles. The upper incisor is very broad (>2.5 mm). The outcrop of the lower incisor is very short (<4.0 mm). The length of the lower incisor is only 77 % of length of the mandible. The third upper molar is very distinct; its tooth loop is sector-like or bean-like. Morphology of the glans penis is very distinct; its proximal baculum is flask-like. The distal base of the baculum is markedly enlarged. The overall outline of the skulls of Bedford's vole is significantly bent. Morphology of the upper jaw teeth of young Bedford's voles is narrow and strip-like. And the lower jaw teeth give the appearance of a contrary "E". All these characteristics of Bedford’s vole differ from species within other genera in the same family. For example, the upper incisors in these comparative species are much narrower (<2.44 mm). In addition, in comparative species the outcrop of lower incisors is longer (>4.5 mm), the length of the lower incisor exceeds 80% percent of the mandible, the outline of the skull is very flat, the base of the proximal baculum is rhombus or round, the distal baculum is stick-like, and the lateral baculum is ossified. The stark contrasts that are apparent in these comparisons clearly indicate that Bedford's vole belongs to a single genus: Proedromys

Key words: Bedford’s vole（Proedromys bedfordi）, Morphology, Taxonomy

摘要： 沟牙田鼠是分布于中国四川西部和甘肃南部的一种罕见小型啮齿动物，迄今标本收藏甚少，种、属地位存在异议，有人认为应并入田鼠属。我们根据四川九寨沟自然保护区采到的16号不同年龄、性别的沟牙田鼠，就其牙齿形态和成年雄性的阴茎结构与其它田鼠类作了比较，发现其成体和幼体在M³和M₃形态上有很大不同。其他重要区别包括：上门齿宽大；下门齿外露部分很短，下门齿总长仅及下颌长的77％左右，远比其他田鼠小；M齿环呈圆弧形或豆形亦很特殊；成年雄性的阴茎骨近支烧瓶状，远支基部膨大与田鼠类差别很大。结果表明：沟牙田鼠属是有别于田鼠属的有效属。

关键词: 沟牙田鼠, 形态, 分类