112 ON THE LITTORAL FAUNA OF N. E- AUSTRALIA, 



is stunted in a cold climate to a fourth its size, and readies its 

 maximum of development in tlie tropics. 2. Littorina pyramidata 

 which, reaches its maximum of development in the temperate 

 seas of Australia, and is dwarfed and deformed in the tropics. 

 3. AcmcBa septiformis, which ranges through every climate from 

 the extreme of cold to the extreme of heat, and is not affected by 

 climate at all. 



The conclusions to be drawn from these facts are far more 

 important than would aj)pear at first sight. We are accustomed 

 to say that certain shells are tropical in character, and indicate a 

 tropical fauna, and this would appear justifiable as far as the 

 present fauna of Australia is concerned, but when we apply it to 

 geology the conclusions are not by any means so certain. There 

 may be species with a very wide range, and the development of 

 one species which we are inclined to refer to the influence of 

 warmer seas, may be from quite a contrary course. We have an 

 instance of this in Pectuiiculus laUcostatus, Lam., which is found 

 extensively developed in our Tertiary rocks, but principally in 

 the Miocene of Yictoria. It is still found on the coasts of Australia 

 but rarely, and of small size. But its maximum development 

 is now in New Zealand, where it reaches as large a size as any 

 of the fossil forms, but generally in the colder parts of the Middle 

 Island coast. 



We have only one Patella on the coast of Trinity Ba}^, that is to 

 say only one true Patella, with the gills as a fringe round the foot. 

 This is P. tigrina ? Grm., with its very conspicuous, silvery- white 

 nacre. It is a shell of moderate size and not very common, gener- 

 ally preferring the very outermost rocks where it is washed by 

 the spray of even low tides. The older shells are much corroded, 

 one distinguishing feature about the species is the well-defined 

 spathula which is of light brown color, and has even the impression 

 of the tentacles on each side of the head. It would seem as if 

 the spathula is caused by some corrosive action of the mantle on 

 the sheU, because on old shells a slight pressure from the inside 



