WATSON: NOTES ON NOMENCLATURE OF HYGROMIA, HELICELLA, ETC. 281 



of the number of species which had not then been dissected.^ But 

 the fact that there are still some Continental forms of which we do 

 not yet know the affinities is not a sufficient reason for uniting in one 

 group species which are definitely known to belong to different groups. 

 A scientific classification should surely accord with what we do know 

 rather than with what we do not know. 



Trochula Schliiter, and Trochoidea Brown. 

 Messrs. Gude and Woodward reject both of these names for the 

 group of which H. elegans Gmelin is the typical species ; and as 

 Turricula Beck is preoccupied, they consider that the correct name of 

 this subgenus is Xeroclivia Monterosato (1892). Trochula Schliiter 

 (1838) is rejected because of Trochtihts Humphrey (1783), for 

 although the latter name is not valid they say : " Even if Humphrey's 

 names in his ' Museum Colonneanum ' be set aside, the name 

 Trochuliis is so sure to have been quoted in some work that it is safer 

 to suppress it." But, as we have seen when discussing the names 

 Hygromia and Trichia, the Recommendation of Article 36 precludes 

 the rejection of Trochula Schliiter on account of Trochulus Humphrey 

 which differs from it in its ending, even if the assumption that 

 Humphrey's name was rendered valid by quotation prior to 1838 

 should prove to be correct. It is therefore evident that those who 

 wish to follow the Rules and Recommendations of the International 

 Code must use the name Trochula Schliiter in preference to Xeroclivia 

 Monterosato, a name which was not proposed until fifty-four years 

 later. 



The name Trochoidea Brown (1827) is, however, older still; but it 

 is rejected by Gude and Woodward apparently on the ground that it 

 is doubtful whether Brown's Trochoidea terrestre should be identified 

 with H. elegans Gmelin or with H.fulva Miill. A study of Brown's 

 original work seems to show that it was H. elegans to which he gave 

 this name. Brown's two drawings,- it is true, are very badly executed ; 

 but in the explanation which accompanies them he cites both 

 Donovan and Montagu, thus : — "Trochoidea terrestre. Browns MSS. 

 Trochus terrestris, Mont. Test. Brit., p. 2S7. — Don. Brit. Sh., pi. in." 

 Now the three figures on plate cxi in the fourth volume of Donovan's 

 work clearly depict the banded form of ZT. elegans Gmelin, with which 

 his description also agrees, although Donovan falls into the error of 

 thinking that Pennant's Trochus terrestris must have been the species 

 with which he is dealing, Montagu's Trochus terrestris was also H. 

 elegans Gmelin, and not H.fulva MiilL, for he describes it as having 

 a livid-white, conical, umbilicated shell, with a strong keel, a flattened 



I Man. Conch, (second series), vol. ix, 1894, p. 254. - 

 z lllust. Conch. Gl Brit., 1827, pi. xli, figs. 80, 81. 



