MONSTROSITIES OF LITTOR1NA RUDIS. 193 



having the last whorl almost free and cmattached to the body of the 

 shell. Figs. 2 and 3 represent very similar specimens from different 

 points of view. Fig. 1 represents a specimen kindly lent by Mr. 

 Erockton Tomlin, which is sinistral from the apex, and which he 

 found in some drift taken from this Langton Herring shore. There 

 are, I believe, only two or three specimens of this variety known. 

 All these specimens (except that represented by fig. 12) belong to 

 the variety Tenebrosa, and there are found with them in the drift 

 ScroUcularia Tenui, Hydrolia Ulvae Missoa Membranacea, Acer a 

 Bullata, and Truncatella Truncatula, all of which, save the last, are 

 found plentifully alive. No large or full grown examples have 

 been found ; the result of a deviation from the normal form seems 

 to have been fatal to the molluscs at a very early period of their 

 existence. A fair quantity of specimens of these forms have been 

 found, but they are generally so broken that a perfect specimen is 

 scarce. 



Many other interesting forms of Littorina have been noticed 

 from various localities. I have a variety of Littorina Littorea (var. 

 Turrita) from Belfast Loughfwhere it is not uncommon, in which 

 the spire is produced, the whorls inflated, and the suture deep. 

 There is said to be no confervoid weed present in this locality, and 

 Mr. Marshall informs me that all the species found with them that 

 he is aware of are normal in form. This species has also been found 

 sinistral when adult, There are in the collection made by the late 

 Mr. MacAndrew, now at Cambridge, several specimens of Littorina 

 Littorea keeled and depressed, but of the normal colour. Also 

 there are in the British Museum several keeled and turreted forms 

 of Littorina Rudis from Falmouth and Exmouth. All these 

 specimens have the nucleus of the shell regular. 



There is a very interesting colony of Planorbis Corneus, described 

 and figured by Dr. Baudon,* though it should be remembered that 

 this is a freshwater and not a marine species. His figures are very 

 interesting and represent specimens very similar to some of mine. 

 He has been kind enough to furnish me with some notes of his find, 

 * Journal de Conchy liologie, xxxii., pp. 319-22, and pis. viii.-x. 



