124 ON THE LITTORAL FATTNA OF N. E. AUSTRALIA, 



were first figured by Lister, nearl}^ 200 years ago, and types are 

 still preserved in the Linnean cabinet. 



On tlie edges of the reefs Trochus 7iiloticus is very common and 

 of large size. This is a shell of wide range and ancient history 

 like the last. It is found with T. cerideus, Gmelin, which is not 

 so common. All the shell sand is more or less full of Chnjsostoma 

 nicoharica, Gmelin. This also has a wide range. In fact except 

 in the relative abundance of species, we may say that for one 

 third of the shells of the Indian Ocean, there is no difference in 

 what we find on the north-east Australian coral reefs. Cyprea 

 tigris, L., is not very common, but C. arahica, L., C. lynx, L., and 

 C. annulus, L., are all very abundant. The cones are C. litter atus 

 L., (very common) C. marmoreus, L., C. generalis, L., C. hebrceus, 

 L., C. textile, L., and C. capitaneus, L. I made no special search 

 or no doubt I could have extended this list, but I merely wish to 

 record the species which are the most common. 



The bivalves are by far the most prominent part of the 

 moUuscan fauna of the coral reefs. Hippopus maculatus, Chem., 

 is the most common, so common indeed that the reef is thickly 

 strewn with them on every side. It varies in size and in color. 

 I have seen a specimen which was at least ten inches across the 

 valves. The color of the animal varies also. As a general rule 

 it is a dull brown, but very often indi\iduals are found with a 

 fringe of the most brilliant blue or green. The same variation 

 in color is found in Tridacna squamosa, Gm., which is equally 

 common. Sippopus maculatus, lies loose upon the reef, but T. 

 squamosa is attached to the coral rock and requires a considerable 

 amount of care to detach it without breaking the shell. It is not 

 at all unusual to find specimens completely imbedded in the rock 

 in a cavity which allows room for the opening of the shell, but 

 which in other respects fits it exactly. In fact one cannot escape 

 the conclusion that the mollusc must have hollowed out the cavity 

 for itseK. It is not uncommon to see a loose block of dead coral 

 with three or four of these large molluscs imbedded in it, fitting 



