151 



PRESIDENTIAL ADDRESS. 



By G. K. GuDE, F.Z.S. 



Delivered 11th February, 1921. 



CHANGES IN THE CLASSIFICATION OF HELICES DURING 

 A QUARTER OF A CENTURY. 



When Dr. H. A. Pilsbry published his " Guide to the Study of 

 Helices "^ he broke new ground in several directions, and with his 

 masterly grasp of anatomical and systematic details revolutionized 

 the system of classification which until then had obtained. Numerous 

 species, subgenera, and sections placed in Helix by various authors 

 were transferred to other groups, and several new genera and 

 subgenera created by him for the reception of many other forms. 

 The genus Helix was reduced to some 300 species, while the other 

 genera totalled over 3,700 species. The number of species of all 

 Helicid genera now known exceeds six thousand. Several previous 

 attempts had been made, notably by Albers, von Martens, Pfeiffer, 

 and Clessin, and, for the Palaearctic forms, by Westerlund. The 

 absence of anatomical data in many cases operated, however, 

 against a rational grouping of the many genera and subgenera 

 proposed by various authors. 



That the whole of this new classification should be accepted 

 without dissent by all students of Mollusca was not to be expected, 

 since in several cases anatomical data were still wanting, and many 

 genera and species were only tentatively allotted a place in the 

 system. Dr. Pilsbry himself has since made a number of corrections 

 in the light of subsequent anatomical investigations, while many 

 other authors have made contributions of a similar nature. Several 

 genera have been removed to other families, many others, again, 

 have been incorporated, among these two large ones — 

 Stwphocheilus and Amphidromus — and a great number of new 

 genera and subgenera have been created. I now propose to 

 enumerate seriatim all these additions to our knowledge of this 

 popular group of mollusca. 



Lieut.-Col. Godwin- Austen in 1898 ^ established Philalanka 

 as a subgenus of Entodonta, but in 1907 ^ he placed it as a subgenus 

 under Thysanota, Alb., at the same time proposing the subfamily 

 Thysanotinae of the family Entodontidae. Thysanota had been classed 

 as a section of Eulota by Pilsbry. The genus numbers twenty-one 

 species. 



In 1914 * I established the genus Glyptaulax for the reception of 

 Helix artificiosa, Bens., placed in Punctum by Tyron, and under 



1 Man. Conch., ser. ii, vol. ix, Nov., 1983-Feb., 1895. 



^ Proc. Malac. See, iii, p. 11. 



' Land and Freshw. Moll. India, ii, p. 190, 



* Fauna Brit. India Moll., ii, p. 14. 



