352 Miscellaneous. 



It seems exceedingly likely that the Petalograpti had a Pliyllo- 

 graptus as a remote ancestor, but the evidence for this is not yet 

 complete, nor can the Author state whether Cephalogra/ptus had a 

 further stage in a form of Dimorphograptus. 



MISCELLANEOUS. 



What are the Names of the Crayfish and Lobster ? 

 By E. I. POCOCK. 



THE hope of being able to supply an answer to the above question 

 gives me the courage at this juncture to intervene in the discussion 

 concerning Astacus and Potamobius started in the ; Annals ' of last 

 December by Prof. Eell ; for, in spite of all that has been written 

 on the subject, it may be doubted whether those who are not 

 specially conversant with the questions of nomenclature that have 

 been raised are any more enlightened as to the correct names of 

 these now famous crustaceans than they were before the contro- 

 versy began. 



It seems to 'me, however, that the question may be set at rest by 

 the application of a principle in nomenclature which is becoming 

 widely accepted amongst systematic zoologists, and will doubtless be 

 universally admitted when our views are a little more coherent and 

 advanced than they are at the present time. It is one of the 

 principles for selecting the type species of a genus when no type 

 has been designated by its author, and may be stated as follows : 

 When the name of a genus is the same as that of one of its compo- 

 nent species, that species is the type of the genus. 



If this principle be applied to the case of the lobster and the 

 crayfish, it will be found that the name Astacus must be attached to 

 the latter, for in both the tenth and twelfth editions of the 

 ' Systema ' Linnaeus called the Swedish crayfish Cancer astacus ; 

 and since Astacus was subsequently used by both Gronovius and 

 Fabricius as a generic term for a group comprising amongst other 

 species the Cancer astacus of Linnaeus, the latter is ipso facto the 

 type of the genus Astacus. Therefore the name of the Swedish 

 crayfish is Astacus astacus (Linn.). With Astacus thus fixed 

 definitely on to the crayfish, Homarus will, it seems, without let or 

 hindrance, resume its place for the lobster, with the specific name 

 gammarus which Linnaeus assigned to it. 



This appears to me to be a sensible and simple solution of this and 

 other similar cases. In the present instance it does away with 

 difficulties arising in connexion with the subsequent actions of 

 Leach, White, Milne-Edwards, and others, and is independent of the 

 selection of the tenth or twelfth edition of the ' Systema ' as the 

 starting-point in systematic zoology. 



In conclusion, there is one little point about which it may perhaps 

 be permitted to me to put Mr. Stebbing right. Erom some words 

 that appear in his contribution to the present discussion it is to be 

 inferred, though perhaps wrongly, that he considers a semi-official 

 system of nomenclature to be in vogue at the Natural History 



