THE RULES OF NOMENCLATURE 365 



from its resemblance to some object, such as a sword or 

 an acorn, and the Latin name of that object has later 

 been applied to a new genus into which the species has 

 been transferred : thus we get Ensis ensiformis (S. V. 

 Wood) and Balanus balanoides (Ranz). Yet again, a 

 character unusual in its genus is taken for the trivial 

 name of a species which is afterwards transferred to 

 another genus in which that character is normal : thus a 

 spiny shell from the Chalk was taken by J. Sowerby to 

 belong to the genus Plagiostoma, and as the only spiny 

 species in that genus it was appropriately called Plagio- 

 stoma spinosum, but later it was transferred to the spiny 

 genus Spondyltts, but the name Spondylus spinosus, though 

 meaningless as a description, serves quite well as a 

 name. 



The original Stricklandian code of 1841 proposed that 

 a name might be changed when it implies a false proposi- 

 tion which is likely to propagate important error. For 

 instance, Hyatt named an ammonite Mantelliceras 

 indianense, a name apparently implying that it was 

 found in the State of Indiana, whereas it actually came 

 from India. It might seem reasonable in this case to alter 

 the trivial name to indiense or indicttm, were it not that such 

 a change might lead to the idea that two distinct species 

 were in question. Really serious cases of this sort must 

 be so few that they can easily be kept in mind, and once 

 we depart from extreme cases we find individual judg- 

 ment introducing uncertainties ; consequently later zoolo- 

 gists have wisely dropped this proposal and agreed that 

 once a name has been published it may not be altered, 

 even by the author himself, except in correction of an 

 evident slip of the pen or misprint. 



The Stricklandian code also proposed that where the 

 trivial name of a species was taken as the generic name 

 for a new genus in which that species was included, the 



