A Further Commentary on New Zealand Molluscan Systematics. By H. J. Finlay, M.Sc.* As originally presented, this paper was under the joint authorship of T. Iredale and H. J. Finlay. It had been suggested and written by the latter after verbal discussion and some correspondence with Mr. Iredale, to whom it was subsequently submitted for revision and extension. Pressure of other work, however, unfortunately prevented Mr. Iredale from carrying out this part of the undertaking, and it has accordingly been agreed that the paper shall appear under a single name. The writer must therefore take all responsibility for its shortcomings, and desires to acknowledge his indebtedness to Mr. Iredale not only for some of the ideas and suggestions contained therein, but also for his generosity in permitting the publication of the paper in its present form.—H. J. F. [Read before the Otago Institute, 11th November, 1924; received by Editor, 31st December, 1925; issued separately, December 23rd 1926. Twelve years ago Iredale wrote a “Commentary” on Suter's “Manual of the New Zealand Mollusca” (Trans. N.Z. Inst., vol. 47, pp. 417–497, 1915). Many subsequent notes were drawn up by him in connection with the collection in the British Museum (Natural History), but the war prohibited any sustained study and consequent publication. Examination of Roy Bell's Australian material developed a few cases of Neozelanic interest, and some have been published in the Report on the Twofold Bay collection (Proc. Linn. Soc. N.S.W., vol. 49, pp. 179–278, 1924), hereafter referred to as “Iredale (1924)”. In 1923 Iredale returned to Australia, and his intensive collecting around Sydney has been instrumental in indicating some relationships not previously recognized. For some years the present author has been studying Recent and fossil New Zealand Mollusca, and many series of lineage forms linking up fossil and Recent shell-groups have been determined. Data have been procured proving the ancient development and separation of apparently closely-related Recent forms, and I would endorse Martin's dictum, “The species with which one has to deal in palaeontology are no physiological but morphological species. The individuals of such species of mollusca… agree in a single anatomical element, the shell. Such an agreement may exist, however, while other elements are absolutely different.” (Martin, 1917). One may cite in illustration of this the heterogeneity of the Minolioid shells, the Buccinoid Mitras, and especially, in connection with New Zealand species, the case of Diloma nigerrima Sow., considered later. Little close relationship in Recent times is determinable between the east Australian and Neozelanic molluscan faunas, relations whenever recognized being usually with the latter and Tasmanian species. A “List of Recorded Relationships between Australian and New Zealand Mollusca,” dealing chiefly with the fossils, has