The 1837 edition accidentally omitted the preposition under in this passage. The resulting “were called that head” was copied into the first three British editions but not the 1840 edition. The second printing of the 1852 British edition restored the under, most probably by reference to the 1840 edition. Apparently, the reading “were called that head” did not seem that difficult. For a discussion of the use of the term head with the meaning ‘category’, see under Jacob 1:4. The use of under with head is found elsewhere in the text: “and under this head ye are made free” (Mosiah 5:8). The critical text will, of course, maintain the phrase “under that head” here in Alma 3:10.
Summary: Maintain in Alma 3:10 the occurrence of under in “were called under that head”.