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NOTES ON PROSOBRANCHIATA. 

 No. W.—LITTORINACEA. 

 By H. Leighton Kesteven. 



(Plate XXX.) 



When studying the affinities of Fossarina (9), I found that 

 Risella differed in anatomic characters from Littorina, the type 

 genus of the family, to which, in the past, it has been assigned. 

 I have since studied its anatomy from actual dissections and 

 from sets of serial sections, kindly prepared for me by Messrs. 

 J. P. Hill and R. Greig Smith. My thanks are also due to Mr. 

 C. Hedley for many useful suggestions. I have also dissected 

 Tectarius and Littorina. As a result of comparing the anatomy 

 of these with other Tsenioglossa, I have found it advisable to 

 reclassify the Littorine groups thereof. It will be as well to 

 state my conclusions first and discuss them in detail afterwards. 



I have taken as my base Fischer's classification (4, pp. 707-711), 

 and have altered it in the following manner : — 



Superfamily LITTORINACEA. 



Family LITTORINID^.* 



Containing those genera enumerated hereunder by Fischer, 

 with the exception of Fossarina (which in my paper above 

 referred to has been shown to be a Trochid), Risella and Echinella. 



* In defining Littorinidae thus I have had to take a good deal for granted, 

 since there have been no dissections of several of the genera published; nor 

 have I been able to study the soft parts of any but Australian members. 

 I have been unable to obtain even the shells of some of the genera. It is 

 probable that, as our knowledge of Prosobranchiate anatomy increases, 

 several of them will have to be removed. 



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