CHAPTER LVII: THE LIMPETS. TENT SHELLS 



Family AcM/tiOy^ 



Shell bowl-shaped, conical, with the apex a little in front 



of the middle, not spiral at any stage of development; with 



distinct internal border of the aperture; lining never iridescent; 



a free branchial plume at left above neck; radula lacks middle 



teeth. Mostly marine mollusks living on seaweed and rocks 



near shore. 



Genus ACM/EA, Eschs. 



The structure of a limpet may be made out with little trouble, 

 for an animal that lives in such a shell cannot be very secretive 

 as to the arrangements of its "in'ards." Slip a knife blade under 

 the shell and it rolls off the rock into your hand. The branchial 

 plume, extended at the left side of the neck when the limpet 

 travels, is drawn in, but not concealed. The central, muscular 

 disk is the foot, which has very remarkable tenacity when affixed 

 to a rock face. In front the short head with its mouth and pair 

 of tentacles appears; encircling all is the mantle border, lining 

 the shell. From the mouth of a dead specimen draw the toothed 

 radula, and examine the series of teeth under a good magnifier. 

 This is the organ which rasps the algae from the rocks. 



What a safe shelter is the arching roof under which this mol- 

 lusk lives ! Yet to breathe, the shell must be slightly lifted. This 

 gives watchful and hungry crabs and sea birds their only chance to 

 catch limpets unawares. They are quick to save themselves when 

 warned. Br.t many pay for their inattention with their lives. 



Should the strongest arm endeavour 



The limpet from its rock to sever, 



T is seen its loved support to clasp 



With such tenacity of grasp 



We wonder that such strength should dwell 



In such a small and simple shell. — IVordsworth. 



The Tortoise-shell Limpet (A.iesiudinalis,Mu\\.) , common 

 on the Maine and Alaskan coasts, reaches iV inches in length, 



231 



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