Foraminifera note details
ICZN 30.1.2. a genus-group name that is or ends in a Greek word transliterated into Latin without other changes takes the gender given for that word in standard Greek dictionaries; The suffix -trema comes from the Greek τρῆμᾰ (neuter): hole, aperture, perforation. Hickson (1911, p. 451) stipulates: "The specific name of the only species of the genus Homotrema should be “rubrum” (Lamarck)." clearly indicating that the genus is neuter.
Hickson, S. J. (1911). On Polytrema and some allied genera. A study of some sedentary Foraminifera based mainly on a collection made by Prof. Stanley Gardiner in the Indian Ocean. [The Percy Sladen Trust Expedition to the Indian Ocean in 1905 under the leadership of Mr. <em>J. Stanley Gardiner. Volume III.] Transactions of the Linnean Society of London (2, Zoology.</em> 14(3): 443-462.