ICZN article 30.1.4.4. stipulates: "A compound genus-group name ending in the suffix -ites, -oides, -ides, -odes, or -istes is to be treated as masculine unless its author, when establishing the name, stated that it had another gender or treated it as such by combining it with an adjectival species-group name in another gender form."
Cushman (1917) did not give any indication about the gender of Globigerinoides but quoted the type species as G. rubra.
He seems to have constantly used Globigerinoides as a feminine genus in his publications.
Authors describing new species and subspecies have variously considered Globigerinoides to be a feminine or a masculine genus.
Nevertheless the recent publications give at a great majority the genus as masculine.
Considering the confusion about the grammatical gender, the WoRMS editors are applying the general ICZN rule and consider Globigerinoides to be a masculine genus.