As explained by Mr. E. R. Waite in the Introduction to this Memoir, the object of the Trawling Expedition was primarily the capture of food fishes, biological investigation taking a second place. Except a few of great bulk, the Mollusca, by reason of their small size, escaped the meshes of the trawling net. At two stations only, Nos. 13 and 49, did our colleague succeed in procuring small quantities of the sea bottom. These have yielded most of the material dealt with in the following pages.
Since the "Thetis" reached in water from 20–80 fathoms, a region almost unknown to Australian investigators, it follows naturally that a high percentage of the species taken is new to science. The known species are those which extend upwards to the littoral zone on this coast, or those which frequent shoal water in Tasmania. To the latter apply the law enunciated by Forbes, that "parallels in latitude are equivalent to regions in depth." This truth so amply demonstrated for the northern hemisphere, is here first established for Australian waters.
My acquaintance with Australian Tertiary mollusca is too slight to permit a full comparison, but I am within the mark in stating that the collection here dealt with presents a closer relation to the Tertiary fauna than any recent shells yet examined. Survivors specifically unchanged are Trigonia margaritacea, var. acuticostata, McCoy, Nucula obliqua, Lamarck, Limopsis tenisoni, Ten. Woods, and Sarepta obolella, Tate. The fossil Pecten polymorphoides, Zittel, is hardly to be distinguished...