Guadalcanal-Nggelic (GN) is one of two branches of the Southeast Solomonic subgroup of Oceanic. Citing phonological and lexicostatistical evidence, several scholars have proposed an internal classification of GN in which Bugotu is an isolate, coordinate with a branch consisting of all remaining languages including Gela. This paper will argue that there are stronger grounds for an earlier and contrary hypothesis of mine that Bugotu and Gela form a closed, second-order subgroup of GN, here labeled Nggelic. The existence of longstanding dialect networks in the GN area means that determining the most probable directions and sequence in which particular innovations spread requires considerable interpretive work. The distribution of morphological innovations points to an early divergence between a dialect area ancestral to the Nggelic and North and West Guadalcanal languages, on the one hand, and a dialect area ancestral to the Southeast Guadalcanal languages, on the other, the two areas being separated by the rugged central mountain range. The fact that there are some lexical isoglosses shared by certain Southeast Guadalcanal languages with North and West Guadalcanal languages exclusively of Nggelic can best be explained by supposing that, after Nggelic diverged from North and West Guadalcanal, all the Guadalcanal dialects participated in a network of speech communities within which there was considerable but uneven diffusion of lexical items.