398 DR. GWYN JEFFREYS ON MOLLUSCA OF THE [Apr. 16, 



tula, as Mr. G-. B. Sowerby, Junr., and Mr. Reeve have done. As 

 to Terebratulina and Waldheimia, Mr. Davidson some years ago 

 considered both subgenera of Terebratula ; but he is now of opinion 

 that Waldheimia is a distinct genus, because (to use his own words) 

 " the recent or living species are but a handful, in comparison with 

 the fossil species, and these last must be taken into account when 

 making divisions of the class, and it would be a very great advantage 

 to retain such divisional groups, which have so many distinguishing 

 characters, and are so numerous." I fully admit the force of his 

 reasoning on the first mentioned ground, and that all fossil species 

 must be included with recent species in the same scheme of classifica- 

 tion ; but the latter ground, which depends on the validity of distinc- 

 tive characters and the relative number of species, is not, in my opinion, 

 equally tenable. It is notorious that Terebratulina and Waldheimia 

 gradually pass one into another, as well as into the main or typical 

 genus Terebratula ; and I contend, with great deference to Mr. 

 Davidson's more experienced judgment, that it would be more ad- 

 vantageous to science not to multiply unnecessarily the generic 

 names, when fewer would answer every purpose. It cannot be pre- 

 tended that such names have any value beyond being mere symbols 

 or signs to distinguish and recognize certain groups ; they are, and 

 must be, quite artificial and arbitrary. The question of number of 

 species in a genus does not appear to me of much importance. Take 

 for instance the genera TJnio, Helix, and Bulimus, each of which, 

 even in a restricted sense, contains several hundred species. It may, 

 of course, be possible to divide these and other well-stocked genera 

 into more genera, each containing an equal number of species ; and 

 the same method might be adopted with respect to the species, and 

 even with respect to the individuals of every species. But that would 

 hardly be a scientific proceeding ; and it might cause much con- 

 fusion or needless trouble. All genera ought to be equivalent 

 as regards distinctive characters, not as regards the number of 

 species. 



I will now venture to suggest an arrangement of the few Brachio- 

 poda which are at present known to inhabit the European seas, and 

 which comprise the species procured in the 'Lightning' and 'Por- 

 cupine ' Expeditions. The following Table gives not only the names 

 of the species and principal varieties, but also the range of depth 

 and the places where they have been found fossil in the Tertiary 

 formation. 



