(syn. Pachyptila Ϯ Slender-billed Prion P. belcheri) Gr. ἑτερος heteros different; genus Prion Lesson, 1829, prion; "GENUS - HETEROPRION, NOV. ... Type - H. belcheri, sp. n. ... I have consequently restricted Pseudoprion to the P. ariel (= P. turtur) group, which I find to differ essentially from the narrow-billed Prions grouped about P. desolatus, and have therefore introduced the above genus to include the medium-billed Prions, and have named as type the thinnest-billed one, H. belcheri, as this shows best the great difference between this group and the P ariel (= P. turtur) group. The species of this genus have the bill shorter and narrower, the wing shorter, and the tarsus shorter than the members of the genus Prion" (Mathews 1912).