MARSHALL: ADDITIONS TO "BRITISH CONCHOI.OGY." 295 



Pleurotomidae Loven. — The nomenclature of this extensive 

 family has got into a thoroughly chaotic state, and badly wants 

 mending or ending. So many fancy genera and sub-genera, of no 

 scientific value whatever, have now been introduced into it, that 

 authors are puzzled where to assign new species, and no sooner is a 

 group or section defined than a new species arises to upset it, a 

 feature which is strikingly apparent throughout the Challenger Re- 

 ports. Nearly every successive writer seems to agree only in one 

 thing, and that is to ignore his predecessors and adopt a fresh system 

 for himself. Only one of two courses (both extremes) seems open to 

 the naturalist, as distinguished from the " literary" conchologist, and 

 that is to make a distinct genus of nearly every species, as is done by 

 some writers, or in despair to lump them together under one or two 

 genera, as is adopted by others. The Rev. R. Boog Watson thinks 

 that the "sculpture and form of the apex may probably serve as the 

 safest basis of classification in the whole group," ^ while Dr. Gwyn 

 Jeffreys more plainly says that " there ought to be at least one dis- 

 tinctive and fixed character, and no transitional or intermediate 

 forms." ^ The pretty way in which this family has been tinkered is 

 strikingly shown in the Challenger Reports by Boog Watson, who 

 says, for instance, in describing his Pleurotoma viacra — " I have put 

 this and the two following species under Mangelia, not because they 

 at all agree in sculpture with that group, for they do not, but because 

 the apex agrees better with the apex of Maiigelia than it does with 

 that known to me in any other of these very perplexing and badly- 

 defined groups. I do not believe that this and many other species 

 can remain where I have put them, but as the entire family is in 

 process of disintegration, they may fare with the rest."^ 



In the face of such evidence as this, naturalists who are indifferent 

 to "systems," or the wrangles over nomenclature, may pursue the 

 even tenor of their way, trusting to the inevitable reaction that always 

 follows extremes. Object-lessons are not wanting to show where 

 these extremes inevitably lead when pursued " to the bitter end ! " 

 The whole difficulty in this and other genera has arisen from a few 

 writers having abandoned or failed to grasp the fair meaning and 

 limits of a "species" or "genus," and no improvement can be 

 expected while these terms mean one thing to one man and another 

 thing to another. Notwithstanding the fact that the British Associa- 

 tion Rules on Nomenclature have been promulgated for so many 

 years, the confusion tends to become worse and worse, and unanimity 

 is further off than ever. 



1 Challenger Gastropoda, p. 360. 



2 New and Peculiar Moll., Ann. Mag. N. Hist., 1877, p. 331. 



3 Challenger Gastropoda, p. 345. 



