MOLLUSCA. 



PART I. 



By Charles Hedley, 



Concholoiiisb, Australian Museum. 



BRACHIOPODA AND PELECYPODA 



PART I. 



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 pro- 

 curing 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. 

 acuticnstata, McCoy, Niicula obliqua, Lamarck, Limopsis tenisoni, 

 Ten. Woods, and Sarepta oholella, Tate. The fossil Pecten 

 polymorphoides, Zittel, is hardly to be distinguished from 



* Forbes— Eep. Brit. Assoc, for 1843 (1844), p. 175. 



