The British Species of Trivia: T. arctica and T. monacha

Abstract

The two forms of Trivia which are recorded from Plymouth (Marine Biological Association, 1931) have hitherto been regarded as one species (Trivia europea), but recent researches (Peile, 1925; Pelseneer, 1932) have shown them to be distinct. Peile calls the two species Trivia monacha (Da Costa), with the spotted shell, and Trivia arctica (Montagu), with the unspotted shell. Pelseneer calls them respectively Cyprœa (Trivia) europœa L. and Cyprœa (Trivia) arctica Montagu. A closer investigation at Plymouth fully bears out the conclusion of the above-mentioned workers that there are two species and the fact, brought forward for the first time in the present paper, that the larvæ are also distinct makes the determination doubly sure.