1. The vitamin ₍₁₂₎ content of the Mollusk (Arca subcrenata) and its extr-action methods have been studied. The results obtained indicate that the vitamin B₍₁₂₎ content of the fresh meat of Arca subcrenata is 65～85r/100g., of its brothobtained during processing, 0.20～0.30r/ml. and of the extractive of its meat0. 25～0. 40r/ml. 2. The vitamin B₍₁₂₎ extracted from Arca subcrenata consists of needle-shapercrystals of dark red color. Its three absorption peaks are found at 278.3m^μ,361.0 m^μ, and 550.0 m^μ. The ratios of absorbency are: A361/A278=1.72, A361/A550=3.25 It was confirmed that the characteristics of vitamin B₍₁₂₎ crystals extractedfrom Arca subcrenata well agree with the descriptions in Chinese PharmaceuticalCode (1963).