NO. 8 OI'lxXJONS 124 TO l^T, 15 



and it was known to them, and so stated, that several of d'Orbigny's 

 specimens had been described and figured by later authors, notably In' 

 M. Boule. 



The opinion expressed by Mr. W. C. Mendenhall and many paleon- 

 tologists of the United States Geological Survey and the United States 

 National Museum is not perfectly clear. It says that those of d'Or- 

 bigny's species " that have been or can be identified should be accepted 

 as valid." This may mean either identified on the basis of d'Orbigny's 

 diagnosis or identified by reference to the type material. The distinc- 

 tion is important, as will appear further in the discussion of Dr. 

 Richter's letter. 



Dr. Richter is the only colleague who defends his position by rele- 

 vant argument. 



1. He maintains that, according to Article 2=,, a species name is 

 validated by a description. Now Article 25 does not say this. It says 

 that a name cannot be valid unless " accompanied by an indication, 

 or a definition, or a description." " Ueber die Qualitiit oder Quantitiit 

 der Beschreibung werden keine Vorschriften gemacht " (Richter). 

 Opinion 52, cited by Richter, says " It is not feasible for the Commis- 

 sion to issue an opinion upon the question : What constitutes an ade- 

 quate description ? " 



All that follows from this is that a name accompanied by a descrip- 

 tion should be considered, but whether the description is sufficient to 

 validate the name is a question to be decided by the reviser. " It is ", to 

 quote the discussion of Opinion 52, " entirely a zoological not a 

 nomenclatorial question." 



Opinion 52 has, lunvever, a direct bearing on d'Orbigny's " Pro- 

 drome ", because it states that the type locality "is to be considered 

 as an important element in determining the identity of species." If in 

 this we intercalate the words " and/or type horizon " we have a restate- 

 ment of the principles on which d'Orbigny worked, as fully ex- 

 plained in the introduction to the " Prodrome." 



2. Richter says very truly that a diagnosis which would be inade- 

 quate to-day may have been adequate when it was drawn u]). This is 

 a view that I have urged repeatedly. But it does not follow that the 

 diagnosis ivas adequate. 



On the assumption that a diagnosis even today may be inadequate, 

 Richter concludes that examination of the holoty])e is essential. T 

 should not like to say anything that would seem to suggest the con- 

 trary. "An jeden Typus hangt der Artname unabiinderlich ", is a 

 principle that cannot be urged too strongly ; but it must not be taken 

 to relieve authors from the necessity for drawing up adequate diagno- 

 2 



