34 



C. HEDLEY. 



viviparous. Both in habit and life history these four seem 

 to represent stages in adaptation to a land existence." 



On this coast the littorinoids in ascending order are: — 

 Bembicium melanostoma, Melaraphe acutispira,M.infans, 

 M. mauritiana, Tectarius pyramidalis, and Melaraphe 

 scabra. It would be interesting to prove if Tattersall's 

 generalisation connecting larval history with beach horizon 

 holds good in Australian seas also. 



In his charming account of the animal ecology of the 

 Cold Spring sand-spit, Prof. O. B. Davenport 1 relates how, 

 near New York, Littorina palliata clings to the stems of 

 the marsh grass, Spartina polystachys, and how near New 

 Orleans L. irrorata climbs the rushes. He suggests that 

 the lack of a siphon exposed Littorina to the danger of 

 suffocation by mud, and that escape from the mud induced 

 a habit of climbing. Thus it started on the road to adap- 

 tation to a terrestrial life — "a road that the Pulmonates 

 must have travelled long ago." 



Fig. 3. Avicennia branch supporting sea-snails, Melaraphe 

 scabra, on the leaves. 



1 Davenport, Decennial Publ. Univ. Chicago, x, 1903, p. 168. 



