378 TELLINID^E. 



fold being less deep in the latter form : S carles Wood, 

 however, shows, in his ' Crag Mollusca/ that the extent 

 of this mark depends on the comparative tumidity of 

 the shell in many species of Tellina and allied genera. 

 The last-named author has properly adopted the spe- 

 cific name balthica. It was at one time said that all 

 geographical or local names are objectionable ; 'and 

 entertaining this opinion I even went the length of 

 substituting fresh names whenever they occurred in the 

 List of British Pulmonobranchous Mollusca, published in 

 the 'Transactions of the Linnean Society/ But that 

 was more than thirty years ago ; and I have since been 

 convinced that the objection to all such names is not 

 tenable. The Committee appointed by the British 

 Association to consider the subject of Zoological nomen- 

 clature did not even recommend that they should be 

 entirely discontinued in future. In the present in- 

 stance the word balthica is not only correct, but com- 

 memorative of the original discovery and of the habitable 

 conditions which belong to the species. Although it 

 does not tell the whole truth, there is no falsehood in- 

 volved in the use of it, nor can it mislead any one. The 

 size of my largest specimens from open bays, where the 

 sea- water has the usual degree of saltness, is an inch in 

 length and one and a quarter in breadth. Clark ex- 

 pressed an opinion that the animal " differs greatly 

 from the typical Tellina in the branchial plate and cha- 

 racter of the palpi, and thick obtuse foot." Mb'rch has 

 referred this species to the genus Macoma (according to 

 Gray Macroma) of Leach. 



Da Costa gave it the appropriate specific name of 

 rubra ; and besides being the T. solidula of Pulteney, it 

 is the T. carnaria of Pennant (but not of Linne), Psam- 

 mobia fusca of Say, and has four or five other less- 

 known names. 



