THE RULES OF NOMENCLATURE 359 



fusion for the following reason : the early palaeontologists 

 recognized two ways of dedicating a species to a man, 

 thus d'Orbigny named two ammonites Ammonites sauzei 

 and Ammonites sauzeanus. Many modern palaeontologists 

 insist upon altering all names of the latter pattern into 

 the former, a proceeding creative of much confusion. 

 Whatever rule may have to be kept for the future it 

 best to retain names of old date unaltered in form. 



If a sub-species or variety needs to be distinguished, 

 its varietal name should be written immediately after the 

 trivial name, as Agnostus pisiformis obesus ; but many 

 authors prefer writing Agnostus pisiformis var. obesus. 

 When a species can be traced, with gradual changes, 

 through a number of zones, each zonal form is called a 

 mutation, and may be denoted by the symbol of its zone 

 (e.g. Productus concinmis Sowerby, mut. D 2 ) or by an 

 adjective (using mut. instead of var.) 



In view of the mistakes that may arise from over-hasty 

 identifications of a known species at a new locality or 

 horizon, modern palaeontologists frequently make use of 

 qualifying or cautionary terms. Their lists frequently 

 contain such records as Hildoceras cf. bifrons (Bruguiere) 

 or Productus aff. productus (Martin). The first means "a 

 species of Hildoceras very much like bifrons but probably 

 not exactly identical with it"; and the latter "a species 

 of Productus which is certainly not identical with P. pro- 

 ductus, but appears to be genetically related to it." 



As to the mode of writing or printing specific names, 

 the following rules should be most strictly adhered to : 

 (i) A generic name should always bear a capital initial 

 letter; (2) a trivial name should always bear a small 

 initial letter* ; (3) when a generic or specific name comes 



* To this last rule most continental authors allow an exception 

 in the case of trivial names derived from a personal name, but the 

 tendency in England is to make the rule absolute, thus writing 

 Asaphellus homfrayi in spite of the fact that the trivial name was, 

 given in honour of a Mr. Homfray, 



