A freshwater red alga, Batrachospermum arcuatum Kylin, is recorded for the first time to the freshwater algal flora of Taiwan. It was found attaching on submerged stones in a clean river in Yuanshan Village, Yilan County. In addition to describe the morphological and reproductive structures of B. arcuatum in detail, we also used rbcL sequences to confirm its phylognetic relationship to other species of Batrachospermum. 本文報導一種臺灣新紀錄淡水紅藻弧形串珠藻，此種藻類生長於臺灣宜蘭縣員山鄉清澈溪流的石頭上。文中除對於此種藻類的形態作詳細描述外，也以葉綠體二磷酸核酮糖羧化酵素大次單位基因(rbcL gene)序列確定其親緣關係的分類地位。
