264 JOURNAL OF CONCHOLOGY, VOL. 15, NO. 9, MAY 1ST, I918. 



Remiform. — Clausium somewhat truncate, produced at the base, 



much resembhng the base of an oar, as in Megalophcediisa. 



Plate 5, fig. 10. 



In order to compare specific differences in the clausium, it seems 



to be necessary to establish terms for the different parts. The most 



characteristic aspect of a clausium is the mtertial one. The point of 



juncture with the columella may be called the proxunal end ; the 



base, the distal end. The term pedicle is familiar, and signifies the 



narrow elastic filament which encircles the columella. The lower 



broader portion I would term the spatula. The inner margin of this 



is that side of the spatula which, in the closed position, lies nearest 



to the columella, and which in Alopia and Claiisiliastra terminates 



at the base in the inner lobe. The outer margin is the opposite side, 



much shorter in extent, terminating in the outer lobe in Alopia., and 



interrupted by the notch or orifice in Clausiliastra. Plate 5. 



ALOPIA, H. AND A. Adams, 1858. 



For much of the material upon which the following notes are based 

 I am indebted to the Rev. Dr. A. H. Cooke, M. A., F.Z.S., who has col- 

 lected largely in Transylvania and Western Roumania, the home of 

 Alopia.^ It is everything in work of this kind to have authentic and 

 correctly localized specimens. 



Alopia possesses a clausium which is small in comparison to the 

 size of the shell, in spite of the fact that it occupies a position very 

 close to the aperture, so near indeed that both lobes of the spatula 

 are visible externally. The size of a clausium depends on the position 

 and form of the lamella-inferior and lamella-subcolumellaris,- but more 

 especially in the presence of the plica-lunata, which runs parallel to 

 the latter along the body-whorl of the shell. When this is present, as 

 in Alopia, Herilla, etc., the effect is a reduction in the size of the 

 clausium. When obsolete or nearly so, there is a corresponding 

 widening in the spatula, which is often truncate or broadly-shouldered 

 at the junction with the pedicle. In Alopia this junction is continu- 

 ous, that is to say there is not at any point any character which would 

 enable us to fix the limit of either pedicle or spatula. 



There is also in Alopia the extraordinary fact that certain species 

 do not possess a clausium at all, and examination shews that in these 

 species the internal structure of the shell is either primitive in type 

 or else has undergone considerable modification. In a non-clausiate 

 species the axis of the columella continues in a straight line as far as 



1 The Distribution and Habits of Alo.pia, by A. H. Cooke ; Proc. INIalac. Soc, vol. x., p. 90. 



2 Smith and Woodward, op. cit. - 



