448 Rev. Canon Norman on the 



et d'autre, les bords de l'ouverture soient reunis circulaire- 

 ment." 



Thus, though Lamarck had at this time separated these 

 genera, he still saw fancied alliances, and therefore points out 

 differences. 



Upon the whole matter Deshayes, in his observations under 

 Delph inula, writes : — " Lamarck rassemblait en un seul genre, 

 sous le nom de Cyclostome, tous les coquilles a ouvertures 

 ronde et entiere. Depuis, Draparnaud reduisit aux seules 

 especes terrestres * le genre Cyclostome de Lamarck ; et ce 

 savant zoologiste dans ses memoirs snr les fossiles des envi- 

 rons de Paris, adoptant l'opinion de Draparnaud, proposa le 

 genre Delph inule pour les especes marines de son ancien 

 genre Cyclostome." 



Next we come to the history of Pomatias. Hartmann, 

 wishing to divide the genus Cyclostoma — as understood in 

 1821 — and at the same time not wishing to change that well- 

 established name, very wisely employed the genus Pomatias, 

 R. Studer, for the section which he desired to separate and to 

 name. He was perfectly justified in doing this, because Studer 

 had included in his Pomatias two species, U P. elegans" and 

 " P. variegatus, a new species ; " to this second species there- 

 fore and its allies Hartmann restricted the name Pomatias f ; 

 and the genus is by most authors properly referred to Studer 

 and not to Hartmann. 



But to pass from a particular to a general subject, I espe- 

 cially desire to call attention to a rule of nomenclature only 

 too often altogether overlooked or most wrongly applied, 

 llule 10 of the British Association u Rules of Zoological 

 Nomenclature'" runs thus: — 



'' §. A name should be changed which has before been 

 proposed for some other genus in zoology or botany, or for 

 some other species in the same genus, when still retained for 

 such genus or species." 



The part of the rule which I wish to emphasize is contained 

 in the words which I have italicized. The object of the rule 

 is that the same name should not he in use for two genera at 

 the same time. Jt follows that if an earlier name is obsolete, 

 say Cyclostoma, a subsequently described genus bearing the 

 same name may be employed. 



* By " terrestres : ' Deshayes means non-marine, for Draparnaud inclu- 

 ded the freshwater operculated univalves now referred to Bythinia, Palu- 

 dina, &c. under his Cyclostoma. 



t Westerlund, in his ' Fauna der in der palaarctisehen Region leben- 

 den Binnsnconehylien,' makes Pomatias variegatus, Studer, a synonym of 

 Vomatiaa septemspiraMs, Razoumovsky (1789), as previous writers hud 

 done. 



