Miscellaneous. 411 



synonymy of a species is given, but otherwise a reference to Cotes 

 and Swinhoe's Catalogue of the Moths of India is substituted. 



Touching the sinking of many described forms to the rank of 

 synonyms, doubtless considerable differences of opinion will exist 

 amongst lepidopterists ; Mr. Hampson has used his private judgment 

 in the matter, and, as an experienced collector of Indian Moths, his 

 opinion must bo allowed to have some weight. Without doubt the 

 reduction of spurious species was much needed ; but nevertheless 

 the decision of no one man, however trustworthy, can be considered 

 as final, until the life-historj' of many more species has been studied ; 

 because it is an acknowledged fact that, whereas some families of 

 Moths are remarkable for their variability, others are almost as 

 constant in all their characters. A. G. Butler. 



MISCELLANEOUS. 



New Observations on the Affinities of the different Groups of Gastro- 

 pods {Expeditions of the Yacht ' Hirondelle '). By M. E.-L. 



BOXJVIER. 



Gastropods are divided into two groups according as they are 

 unisexual or hermaphrodite \ the former (Prosobranchia) are further 

 characterized by their decussating visceral commissure in the form 

 of a figure of eight, while the latter (Opisthobranchia, Pulmonata, 

 Pteropoda) are distinguished by their visceral commissure being 

 more or less free from torsion. After a previous study * I had 

 succeeded in partially removing the abnormal hiatus which an 

 incomplete investigation had allowed to exist between these two 

 groups, which I remained convinced must formerly have been 

 united by a transitional form. If this form still existed it could 

 only be found among the oldest Opisthobranchia, the Actseonidae, 

 which made their appearance in the Carboniferous period, and 

 which are represented at the present time by the genus Actceon, of 

 Triassic origin. Investigations which I have made upon specimens 

 of ActcEon solidulus, kindly handed over to me by M. Jousseaume, 

 show that this Gastropod is, as a matter of fact, an ideal tran- 

 sitional form not only between the Prosobranchia and the Opistho- 

 branchia, but also between the latter and the Pulmonata. As I 

 have already published a succinct resume of the organization and 

 affinities of Actceon f, I shall here confine myself to an exposition of 

 the general considerations to which the organization of this animal 

 gives rise. 



* '•'Quelques observations anatomiques sur les Mollusques gast^ro- 

 podes," Comptes rendus de la Society de Biologie, December 17, 1892. 



t Soci^t^ philomathique, seance du 24 d^cembre, 1892, and Soci6t^ de 

 Biologie, stance du 7 Janvier, 1893. 



