Sardinella dayi Regan 1917, the taxonomic status of which has long been uncertain, is redescribed on the basis of 27 specimens, including the holotype. Although Whitehead (1985) regarded the nominal species as a junior synonym of Sardinella jussieui (Valenciennes 1847), the former differs from S. jussieui in having higher counts of gill rakers on the first gill arch (59–77 + 92–118 = 155–190 vs. 49–60 + 88–106 = 137–158 in S. jussieui), a longer head (26.3–29.6% SL vs. 22.7–24.9%), upper jaw (10.9–12.4% SL vs. 9.6–10.7%), and lower jaw (11.5–13.1% SL vs. 10.3–11.7%), a shorter anal-fin base (13.5–16.2% SL vs. 16.7–18.5%), and body scales with numerous pores (pores absent in S. jussieui). Redescriptions of both species are provided.

中文翻译：

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Sardinella dayi Regan 1917 的有效性和 Sardinella jussieui (Valenciennes 1847) (Teleostei: Clupeiformes: Clupeidae) 的有效性

Sardinella dayi Regan 1917，其分类地位长期以来一直不确定，根据包括正模在内的 27 个标本进行了重新描述。尽管 Whitehead (1985) 将名义种视为 Sardinella jussieui (Valenciennes 1847) 的次要同义词，但前者与 S. jussieui 的不同之处在于在第一鳃弓上的鳃耙数量更多 (59–77 + 92–118 = 155 –190 vs. 49–60 + 88–106 = 137–158 in S. jussieui），较长的头部（26.3–29.6% SL vs. 22.7–24.9%），上颌（10.9–12.4% SL vs. 9.6– 10.7%）和下颌（11.5–13.1% SL vs. 10.3–11.7%），较短的臀鳍基部（13.5–16.2% SL vs. 16.7–18.5%），体鳞有许多毛孔（没有毛孔）在 S. jussieui）。提供了两个物种的重新描述。