112 PNEUMONOBRANCHIATA. 



the mantle, are destitute of this covering ; and they 

 have been separated from other shells for this reason. 

 But this is an error arising from the theory that the 

 periostraca of shells is analogous to the scarf-skin of 

 vertebrated animals, instead of its being merely the 

 part, consisting almost entirely of animal matter, that 

 is first deposited by the animal when it is about to 

 enlarge its shell, and which forms the basis of the 

 new part of the shell, afterwards strengthened and 

 thickened by the addition of the chalky matter 

 within it. 



These animals sometimes suspend themselves by a 

 kind of thread formed from the viscid secretion which 

 covers their body ; hence one of the smaller ones has 

 been called Limax filans. 



Swammerdam (Bib. Nat. i. 158. t. 8.) gives 

 some details of the anatomy of one of the species, but 

 recently Mr. Nunneley, in the Leeds Transactions, 

 has given an excellent paper on the comparative 

 anatomy of three of the species, and has shown that 

 there exists a considerable difference in internal or- 

 ganisation between them and the Avion ater. 



I have great pleasure in referring the reader to this 

 paper for the details, and cannot help expressing a hope 

 that other persons residing in the country will be 

 induced to follow Mr. Nunneley's excellent example, 

 and give to the world similar papers on the animals in 

 their neighbourhood. 



* Mantle produced behind ; shell flat. 



Jl. 1. Limax maximus. Spotted Slug. Animal ash, 



variously spotted, with a long white acute keel ; 



he tentacles vinous coloured, and the hinder 



