Though the writer has seen (with a few exceptions) the types herewith detailed an amply sufficient number of times to establish them as types, he does not claim infallibility, for the key he has worked out to these types. It is hoped, however, that it, together with the descriptions and illustrations will enable the student of the hickory galls to become better acquainted with the members of the two groups treated. Britton and Brown’s Illustrated Flora Northern U. S. and Canada, (2nd edition), New York, 1913, has been followed in the matter of plant nomenclature. The following two galls whose makers have been named by Felt have probably not been seen by the writer. Felt’s descriptions are given. They are not included in the key. =Caryomyia thompsoni= Felt. “Globose, thin-walled, long haired, melon-shaped, dia. 2-3 mm.” See my number 23. =Caryomyia antennata= Felt. “Globose, thick-walled, yellowish green or brown. Dia. 4-5 mm.” This description, as far as it goes, would indicate a similarity to C. persicoides Beut. Felt, Jour. Econ. Ent. 4:456. 1911. KEY. The itonid group of galls herewith presented can be distinguished with one exception (No. 33) from the very common Phylloxera galls (Aphididæ) by the fact that the latter forms which are sufficiently small to be comparable in size to the itonids are intercalated in the leaf blade, i. e. the gall extends more or less prominently from both sides of the leaf. The itonids always give the appearance of an appendicular structure attached to the leaf.