EDITORIAL NOTES. 



327 



The most effective method of closure, and the most highly developed, is not 

 that which is shown in the multiplication of plicre, lamella; and lunule, but in the 

 complete blocking of the mouth by a clausilium, which reduces the evaporation of 

 moisture to a minimum, and, working as it does on a sort of elastic strap, answers 

 in fact to an operculum. From the systematic standpoint the clausilium is of little 

 value ; its size, shape, and development may vary even within the limits of 

 individual species. 



These considerations, which amount to an adoption and extension of the views 

 long ago put forward by W. v. Vest (Verh. Siebenb. Ver. Naturw, xviii, 1867, 

 pp. 5-1S) in reference to the presence or absence of a clausilium in Alopia, tend to 

 weaken a system of classification based on the shell alone. Radula investigation 

 discloses the fact that two main groups occur, according as the central tooth is 

 unicuspid or tricuspid. 



The genital organs are that part of the animal which afford the best evidence for 

 classification. They are more readily examined and preserved than other parts, and 

 so yield the best results in the shortest amount of time. The comparative relations 

 of the sexual organs (penis, vas deferens, and to a lesser extent the receptaculum 

 seminis, the retractor muscles, and the diverticula) furnish never-failing and 

 weighty evidence for the establishment of kindred forms and groups. 



The system of classification proposed in the Nachrichtsblatt is somewhat modi- 

 fied from that of the Iconographie. Thus we have : 



ICONOGRAPHIE. 



Genus Alopia H. & A. Ad. (extended) 



Subg. Alopia s. str. 



,, Herilla Bttg. 



,, Medora Vest 



,, Agathylla Vest 



,, Albinaria Vest 



,, Cfistataria Vest 



Genus Serbica Bttg. 



,, Delima Hartm (extended) 



Subg. Delima s. str. 



,, Siciliaria Vest 



,, Car-inizei'a Mldff. 





Nachrichtsblatt. 



Genus 



Alopia ex. rect. mea 



Subg. 



Alopia H. & A. Ad. s. str. 



,, 



Herilla Bttg. 



Genus 



Albinaria ex rect. mea 



Subg. 



Medora Vest 



,, 



Agathylla Vest 



,, 



Albinaria Vest, s. str. 



,, 



Cristataria Vest 



Genus 



Garnieria Bgt. 



,, 



Delitna ex rect. mea 



Subg. 



Mauritanica Bttg. 



,, 



Siciliaria Vest 



,, 



Carinigera Mldff. 



,, 



Delima Vest [? Hartm.] s. str. 



Genus 



Neo serbica n. 



,, 



Triloba Vest 



,, 



Papillifera Vest [ex rect. mea] 



Subg. 



Papillifera s. str. 



,, 



Isabellaria Vest 



>j 



Leucostignia n. 



It will be for the systematist to say how far this extension or " rectification " of 

 long established groups is in accordance with the laws of nomenclature. But in any 

 case the work of Dr. Wagner, accompanied as it is in the Iconographie by many 

 beautiful figures, is a valuable contribution to science. 



A. H. C. 



