A new species of Amygdalum (Amygdalum anoxicolum n. sp.) is described living in the soft green muds of the oxygen minimum zone off the Oman margin in the northern Arabian Sea. It is distinguished by both its shell and anatomical characters. The anatomy is described and discussed in relation to the environment. The presence of haemoglobin is viewed as a direct adaptation to the low levels of oxygen found in its habitat. The observed wide size range of ingested food particles is discussed in relation to the low oxygen environment. The nest building habit is assumed to be a key adaptation to living in soft, high porosity mud. The distribution of the genus is examined in relation to the distribution of known zones of hypoxia in the world's oceans, but no relationship is evident. Amygdalum species are not indicators of low oxygen environments.