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ON THE RADUL^ OF THE BRITISH HELICIDS. (Part I.) 

 By Rev. E. W. Bowell, M.A. 



Read 8th May, 1908. 



Some few years back English malacologists were distinguished for the 

 persistency with which they retained "the old genus Helix,^^ and 

 refused to accept, for ordinary use, the various subdivisions which have 

 been made by writers dealing with larger faunas. In other branches 

 of zoology there has been a similar unwillingness to narrow the genera 

 to which Linnaeus gave the classical name of the animal. But it now 

 seems to be generally recognized that our Helices form the local 

 representatives of a family rather than of a genus, and the system of 

 nomenclature used by Mr. B. B. Woodward in his paper read before 

 the Cunchological Society on January 14th, 1903, is familiar to all 

 conchologists. 



It is the object of this paper to suggest that the study of the 

 radulse of Helicids affords a means of estimating the importance of the 

 subdivisions of the old genus Helix. Some possible misconceptions 

 of this view are here to be anticipated. The actual number of the 

 teeth on any given radula may he a matter of comparatively little 

 importance ; certainly some of the estimates given in the older 

 literature of the subject are at variance with ordinary fact, just as the 

 measurements of shells have in many cases been shown to be. It 

 becomes a question how many of the extreme marginal rows shall be 

 counted as teeth; and in some forms (e.g. Planorhis), though not 

 conspicuously in the Helicids, this is a very difficult question, owing 

 to the presence of numerous rows that consist of basal plates only. 

 Again, the number of teeth at the growing end of the organ, 

 that are reckoned as existent, will largely depend upon the operator 

 and his methods and instruments, and if it be thought necessary 

 to take all into account that are just beginning to be teeth, one 

 will have to add six or seven transverse rows to the ordinary 

 computations. The imperfect rows which always occur at the 

 front or older end of the radula must not be considered as the 

 representatives of complete rows that have formerly existed ; they 

 form a valuable index of the actual number of rows that existed 

 in the embryonic or sub - embryonic stage of the animal's life. 

 Another point that sometimes causes unnecessary perplexity is the 

 question of the existence or non-existence of an endocone when 

 that part of the tooth is apparently reduced to a mere corner, which 

 may be more or less clearly demonstrated by using various kinds of 

 illumination. In all the Pulmonata that have come under my notice, 

 with the exception of the Testacellidae and the Physidae, each lateral 

 tooth possesses a central cusp which is flanked by the more or less 

 prominent folds called ectocone and endocone. The point of first 

 importance to consider seems to be whether this central cusp is itself 

 single, as is generally the case, or double, as in the larger species of 

 Vitrea (laterals) and Helix s.s. (marginal), or Vitrina (both lat. and 

 marg.). In the group now under notice the prevailing characteristic 



