No. 6 (1921) COMMON MOLLUSCS OF SOUTH INDLA 



209 



of the body and it has been surmised that this enables it to anchor 

 itself to rocks. The life-history and habits of this strange crea- 

 ture are still among the mysteries of life awaiting solution. 



The shell is a loosely coiled cylinder, snowy white without, 

 nacreous within. At frequent intervals throughout its length, it is 

 divided into short chambers by thin concave partitions as in the 

 shell of the Pearly Nautilus about to be described. As in the latter 

 each partition is traversed by a tube or siphuncle. This tube 

 passes close to the inner wall of the whorls, whereas in Nautilus it 

 passes through their centre. 



Last of the Indian Cephalopods, but represented solely by 

 shells drifted ashore, is the four-gilled PEARLY NAUTILUS, the 

 sole living representative of a great host of strange molluscs that 

 flourished exceedingly in Palaeozoic times. The Ammonites, though 

 closely related in shell form, are not so nearly akin as the earlier 

 straight-shelled (9r^//^c^n75. Though the shell of Nautilus like that 

 of Spirula is one of the familiar objects of tropic beaches, nothing 



Fig. 61. Pearly Nautilus in the atiitude of crawling (after Willcy). 



was known of its habits until comparatively recently. Dr. Willey 

 was one of the first to throw light on its life-history, and to watch 

 it in captivity. The seas around the islands of the Western 

 Pacific are its headquarters ; there in moderate depths Willey was 



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