Intrusive igneous suites in the southern New England Orogen span in age from the latest Carboniferous to late Triassic (Fig. 1). The Hillgrove Batholith (informal name) constitutes the oldest intrusive batholith within the accretion-subduction complex of the southern New England Orogen. The batholith is defined here as comprising The Hillgrove Supersuite and the Bakers Creek Supersuite (informal name). The Hillgrove Suite was originally defined by Binns et al. (1967) and several member plutons have been added since by Pogson and Hitchins (1973), Shaw and Flood (1981) and Gilligan et al. (1992). The latter definition included 23 plutons including the Blue Knobby, Campfire, Eastlake, Enmore, Gara, Garibaldi, Glenifer, Gostwyck, Henry River, Hillgrove, Ingleba, Kimberley Park, Kookabookra, Murder Dog, Rockvale and Tobermory monzogranites, together with the Abroi, Argyll, Dundurrabin, Rockisle, Tia and Winterbourne granodiorites. The Hillgrove Supersuite as defined here, includes all of these with the tentative addition of the Harnham Grove Porphyritic Microtonalite which has an age (Black, 2007) within error of other members of the supersuite.