26 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



number of sub-families. It is remarkable that tbe most striking 

 differences that do occur within this family are often found among 

 members of the same sub-family ; as, for example, the difference 

 between the shells of Carelia and Planamastra, between the radulse 

 of Abida and Chondrina, and between the genital organs of different 

 individuals of Acanthinula aculeata or Vallonia costata. 



It is not surprising that this family should have a wide distribution 

 and a considerable variation in external form, seeing that it is the 

 oldest known family of land snails. Shells generally assigned to 

 the Pupillidse — Strophites grandceva, Dawson, and Dendropupa 

 primceva (Mathew) — have been found in the Upper Devonian strata 

 of New Brunswick, and other species of the same genera occur in 

 Carboniferous and Permian beds ; and if the Upper Carboniferous 

 shell from Nova Scotia, originally described as Zonites [Conulus) 

 prisons, Carpenter, has been rightly regarded by modern authors 

 as probably related to Pyramidula, it would seem that all the 

 Palaeozoic members of the Stylommatophora that have hitherto 

 been discovered belong to this family.^ This is a point of special 

 interest, because the orthurethrous type of kidney is generally 

 considered, on morphological grounds, to be more primitive and 

 therefore, presumably, more ancient than the type found in the 

 Sigmurethra, the group to which the majority of living snails belong. 



The remaining families of the Orthurethra seem to be more 

 distinct and less closely allied to Pyramidula, Patulastra, Vallonia, 

 and Acanthinula. The family Achatinellidse — in which I would 

 include the Tornatellininse as a very distinct sub -family — differs 

 greatly from all the forms that we have been considering in its 

 extraordinary radula, which resembles that of Athoracophoridse. 

 It is also characterized by its remarkably small albumen gland, 

 while Pilsbry has pointed out that Achatinella differs from Amastra 

 in other constant characters as well.^ The Partulidse is also a fairly 

 distinct family, according to the same author's description.'^ 



Glessula, which Pilsbry placed provisionally among the 

 Orthurethra, is a sigmurethrous genus, very different from those 

 with which we have been dealing, and it is not improbable that the 

 same may prove to be true in the case of Ccecilioides, Ferussacia, 

 and their allies. The radulse of these genera are of the type found 

 in the Achatinidse, and differ widely from the types occurring in 

 the Pupillidae, Achatinellidee, and Partulidse. 



On the other hand, it is possible that one or two other genera 

 of small Heliciform snails, usually assigned to the Endodontidse or 

 the Helicidae, should be placed in or near the Valloniinae, in addition 

 to those with which this article specially deals. Thus, Aspasita, 

 which has generally been regarded as a section of Helicodonta, is 



' B. B. Woodward, Proc Malac. .Soc. Lond., vol, viii, 1908, pp. 73-7. 

 - Op. cit., vol. xxiii, 1915, p. 61. 

 3 Ibid., vol. XX, 1909, pp. 155-60. 



