Geological mapping combined with U-Pb (zircon) dating and petrological work have resulted in revised interpretations of Neoproterozoic plutonic rocks in the southern Cobequid Highlands. The Frog Lake, Debert River, and McCallum Settlement plutons, as well as the western part of the Gain Brook pluton, consist of the same three components in varying proportions: dioritic rocks, tonalitic to granodioritic rocks, and granitic rocks ranging from monzogranite to alkali-feldspar granite. Based on petrographic and chemical characteristics, the dioritic rocks are comagmatic low-potassium tholeiite suite showing Fe- and Ti-enrichment trends. The tonalitic, granodioritic, and granitic rocks display similar chemical trends and constitute a comagmatic calc-alkalic suite. Both the tholeiitic dioritic rocks and the calc-alkalic intermediate to felsic rocks formed in a volcanic-arc setting, but lack of chemical continuity between them indicates that they are not comagmatic. However, mingled relationships and previously published and new U-Pb (zircon) ages indicate that they are the same age and likely formed in the roots of the same volcanic arc at ca. 615-605 Ma. Hence it is suggested that they be collectively renamed the Bass River plutonic suite. In contrast, the Gunshot Brook pluton in the eastern Cobequid Highlands, although apparently of similar age, displays petrological differences and is not included in the suite. The older Economy River Orthogneiss is chemically distinct and likely part of the previously identified ca. 750-730 Ma Mount Ephraim Plutonic Suite. The Bass River plutonic suite is similar in age and chemical character to some plutons in the northern Cobequid Highlands, Antigonish Highlands, and southeastern New England, and these areas may have been originally together, forming a distinctive part of West Avalonia.