296 Proceedings of the Eoyal Physical Society. 



shell. I have not found it beyond Gul- 

 lane shore, where I took a solitary living 

 specimen. It is abundant at the Isle of 

 May (if.). 



Note. — Where a spring of fresh water 

 rises on the shore above low water mark, 

 a little to the east of Granton East Har- 

 bour, a thin form of P. vulgata, pale, and 

 with a silky surface, takes the place of all 

 other forms, and is plentiful. It may be 

 due merely to the influence of fresh water ; 

 but I suspect a corroding quality in the 

 spring. Tectura testudinalis in the same 

 place is worn very thin. If this form of 

 P. vulgata had permanence, its appropriate 

 name would be var. sericea (M.). 



Helcion pellucidum (Linn.). 



Firth of Forth {MB.). 

 Good specimens common on Lamvmria 

 all along the North Berwick coast, and 

 at Dunbar and Cramond Island (Jf ). 

 We have found this species at extreme 

 low water, at Elie, Aberdour, and North 

 Berwick. It frequents the stems and roots 

 of Laminaria. 



H. iiellucidum, var. Icevis. 



Common in the hollow part (or under 



side) of roots of Laminaria at North 



Berwick ; also at Dunbar and Longniddry 



{M.). 



We obtained the variety also at Elie and 



Aberdour, and on the beach in Largo Bay. 



Tectura testudinalis (Mliller). 



Firth of Forth {M'B.) ; beach between 

 PortobeUo and Fisherrow {Metz. and Mey) ; 

 Granton {M.). 



The shell is sometimes an inch long on the 

 Edinburgh shores. The markings vary 

 greatly, and there is a blue form bearing 



