THE LIMPETS. 



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1AXTHINA AND ITS RAFT, (r, The Ilaft ; 0, the Egg-capsules.) 



Porjjita, or in the mid- Atlantic in the wandering islands of gulf-weed. At certain seasons a peculiar 

 kind of membranous float or raft is secreted from the animal, like a crescentic piece of honey-comb, 

 with the cells tilled with air. The egg-sacs, which are not unlike those of the common Whelk, 

 are attached beneath the float, and when the float is complete, and the egg- 

 sacs full, the creature disengages it, and leaves the eggs to be hatched as 

 it drifts about on the surface in the warmth and sunlight. The shells of 

 laidhina are common in the ' Globigerina Ooze. ' They are not unfrequently 

 cast up on the shore on the west coasts of Ireland and of Scotland, and even on 

 the Shetland and Faroe Islands. They are not, however, inhabitants of the 

 northern seas. They are drifted along and scattered about by the beneficent IANTHINA COMMVMS. 

 ameliorator, 'the Gulf-Stream.'" (Ckallettyer, Vol. L, p. 119.) 



"The JaHthince," says Dr. S. P. Woodward, "are gregarious in the open sea, where they are 

 found in myriads, and feed on the small blue acalephfe ( Velella}. They are frequently drifted to the 



southern and western British shores, especially 

 when the wind continues long from the S.W. ; 

 in Swansea Bay the animals have been found 

 quite fresh. When handled they exude a violet 

 fluid from beneath the margin of the mantle. 

 In rough weather they are driven about and 

 their floats broken or detached, in which state 

 they are often met with. The capsules beneath 

 the further end of the raft have been observed 



to be empty at a time when those in the middle contained young with fully-formed shells, and those 

 near the animal were filled with eggs. They have no power of sinking or rising in the water. 

 The raft, which is much too large to be withdrawn into the shell, is an extreme modification of 

 the operculum." Six species have been described, from the Atlantic and Pacific. 



FAMILY XXII. FISSURELLID.E. 



The shell is conical and symmetrical, shaped like that of a Limpet, but with the apex curved, the 

 front margin notched, or the top perforated ; muscular scar semicircular, open in front. The animal 

 has its eyes at the base of the tentacles, which are somewhat broad ; the head has a short muzzle ; the 

 anal siphon occupies the notch in the shell in front, or passes through the hole in the summit of the 

 shell ; the teeth are like those of Trochus. It is a vegetable feeder. 



Genus Fissurella* " The Keyhole Limpet " has an oval conical shell, with a perforation in the 

 top ; the surface is cancellated with intersecting lines ; in very young shells the apex is nearly spiral 

 and the perforation in front of the apex, but the hole increases in size, and the summit gradually 

 disappears. The FissurellcK mostly inhabit the laminarian zone, but have a range from low water 

 to fifty fathoms. One hundred and twenty species are described. They are cosmopolitan. 



Genus Macroschisma. In this shell the perforation for the anal siphon is close to the hinder 

 margin of the shell. The animal is far larger than its shell. It is found in the Philippines and 

 West Australia. 



Genus Puncturella. In this little shell the fissure is placed in front of the recurved apex ; 

 the shell is conical, and the surface is furrowed. Two species inhabit Greenland, Norway, and 

 North America. It is also found at Tierra del Fuego, and both living and fossil in Britain. 



Genus Rimnla. The shell in Kimula resembles that in Puncturella, but is more oblong, and 

 the perforation is near the anterior margin. Its habitat is the Philippines, and its range from low 

 water to twenty-five fathoms. 



Genus Ema-rgiiuda.-^ This pretty little cancellated form has no hole in its shell, but the front 

 margin has a deep slit for the anal siphon. Twenty-six species are found living from low water to 

 ninety fathoms on the coasts of Britain, Norway, the Philippines, Australia, &c. 



Genus Parmophorus^ Duck's-bill Limpet. The animal is very large compared with its shell, which 



* Latin, diminutive ofjissura, a slit. t Latin, emaryinata, notched. 



J Greek, par me, a shield, &n<\. phoreus, a bearer. 

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