298 SMART AND COOKE : MARINE SHELLS OF SCILLY. 



species have had the advantage of being determined by 

 Dr. Jeffreys. 

 lanthina rotundata Leach. — Occasionally driven on 'shore 

 from the westward, on the beaches facing south-west. The 

 Scillonians have an idea that they come in at fixed periods 

 of about seven years. The South Wales fishermen about 

 Tenby have the same belief. Sometimes very large speci- 

 mens over I "5 in. square have come on shore ; at other 

 times very small ones, about "3 in. square, make their 

 appearance. Occasionally they have occurred in such 

 numbers that hundreds might have been collected at once. 

 Often years pass without a single one being seen. We 

 were fortunate enough last September to find several speci- 

 mens cast on the beach at the back of Bryher, with animal 

 and float perfect and unbroken. When placed in spirits 

 the animal retires into the shell, drawing the float partly 

 with it, in time the float generally becomes detached, the 

 air bubbles escape, and a mere film of collapsed gelatinous 

 matter is left. The last time previous to September, 1884, 

 that the lanthinm came ashore was in the winter of 1881-82. 



Eulima polita L. — Living in gravel outside Menavawr; rare, 

 E. distorta Desh. — Small specimens, with E. polita, never 



common, but not quite so rare. 

 E. bilineata Alder. — With the preceding; common, but 



small. 

 Natica Alderi Forbes. — Abundant in clean sand at low 



water mark. 

 N. Alderi var. lactea Forbes. — Occasional, with the type. 

 Lamellaria perspicua L. — Crow Sound, only a few 



specimens. 

 Velutina laevigata Penn. — Occasionally found dead in the 



Menavawr gravelly sand. 

 Aporrhais pes-pelecani L — Seldom occurs ; has twice been 



found living on the shore, but never dredged. 



J.C, iv., April, 1S85. 



