COCKERELL AND COLLINGE : CHECK-LIST OF SLUGS. 215 



Limacella. I have found it most perplexing to decide what 

 name to use for this genus, but after much consideration 

 have come back to my original (1890) decision in favour 

 of Limacella. There can be no manner of doubt what 

 Blainville's slug was, all the evidence duly considered ; and 

 his type may be seen any day in the British Museum. The 

 whole question seems to turn on the acceptance or otherwise 

 of the rule, "once a synonym always a synonym" — a rule 

 which is of doubtful value, as it gives an importance to pure 

 synonyms they ought not to have, and prevents their being 

 dropped out of the classification. At first sight, the rule 

 appears to be a convenient one, but its logical outcome is 

 absurdity. For example, if I were at the present moment, 

 without conceivable reason, to propose a new name for the 

 present genus, according to the rule, this name could never 

 be used for another genus afterwards ! That is to sav, an 

 absurd proposal of this sort would bind down zoologists 

 ever after to keep the name in their notes or indices lest 

 they should duplicate it. And if valid genus were given 

 this name the nomenclator might lose its authorship, 

 because he was not aware that I had proposed a useless 

 name years before ! Some present difficulty is got over by 

 the " once a synonym " rule, certainly, but it only heaps up 

 trouble for those coming after. One may imagine the 

 scientific author of the year 2000 on his travels followed 

 by a large van. Passer-by: "How is it you have so much 

 luggage?" Scientific man: "Oh, my luggage is in this 

 hand-bag ; that van contains the volumes of the dictionary 

 of synonyms." 



436. Philomycus pennsylvanicus, Pilsbry in litt., July 5, 1893. 

 A medium-sized species with ribbed jaw. Will shortly be 

 published by its author. 



44S. L.formosensis. I expect this is only a race or variety oibilineaia. 



447. L. chi nen sis. Doubtless Heude's slug is the same, but he 

 says it grows to 6 or 7 cm. long, so my type was immature. 



457. V. frauenfeldi. Probably a synonym of a lie. 



461. V. birmanica. Stoliczka in 1873 suggested that this and 

 V. hasselti might both be synonyms of V. mollis (Onchidium 

 molle, Hass. ). 



4' 3. /'. hasselti. Also in Borneo and Sumatra. 

 464-465. I find I have no note of the locality of these, but I think 

 I have included them in the right series. 



