o.» 



(! iii (h> to the Molliiscn. 



foot. Both the true and false Limpets are littoral and are found 

 ( hi rocks between t ide- marks. They have the power of excavating 

 the surface to which they attach themselves, the secretions of the 

 disk-like foot dissolving away the rock to form a shallow pit, to 

 which the animal is known to return with great constancy. The 

 largest known Limpet (Patella (Ancistromesus) mexicana, Case 7) 

 inhabits the west coast of Central America, its shell having some- 

 times a length of 12 inches. The Limpets are vegetable feeders 

 and live on seaweeds of various kinds, which they rasp with their 

 radulae. That of the Common English Limpet (P. vulgata, '¥ig. 12) 



Fig. 12. 



1. Radula of the Common 

 British Rock-Limpet (Patella vul- 

 gata), natural size. 



2. Two transverse series of 

 teeth: a. median teeth ; b. laterals; 

 c. uncini or marginals. 



Fig. 13. 



Pleurotomaria adansoniana. Case 9. 



-} natural size. 

 From The Cambridge Natural History, 

 by permission of Messrs. Macmillan & Co. 



is longer than the shell itself, and is armed with as many as 

 1,920 hooked teeth in 160 rows of twelve each. The Limpet is 

 commonly used for bait in the sea-fishing off the Scottish coast. 

 Some Limpets, such as P. compressa, P. mytilina, &c, are found 

 on the stems of floating seaweeds, and have the shells usually 

 thinner and smoother than the Rock-Limpets, which have to 

 resist the fury of the breaking waves. 



The second sub-order, the Rhipidoglossa, is so called because 

 the teeth of the radula are arranged like a fan. It includes the 

 remaining Aspidobranchia. 



The ' Keyhole Limpets ' and ' Slit Limpets ' (Fissurellidae) 

 resemble in external shape ordinary Limpets, but have the shell 



