306 JOURNAL OF CONCHOLOGY, VOL. l6, NO. 9, JUNE, I922. 



No internal plicae are present in any of these species, but in haueri 

 there is a small lamella superior and faint traces (in some forms only) 

 of a lamella inferior. 



In glauca the lamella superior is fairly strong, but the lamella 

 inferior is still somewhat more of callus than a fold, and is withdrawn 

 internally. 



In livida and deaniana both lamellse are, as a rule, well-developed,^ 

 and the lamella inferior stands out well on the columella. See pi. ix, 

 figs. 5, 6, 7, 8. 



I doubt whether the new section Ithyption proposed by Mr. Dean 

 (Journ. of Conch., xv, p. 265, 1918J is necessary or desirable. He 

 distinguishes it " by the absence of a clausium, by the absence or 

 modification of the lamellae or plicae, and by the relatively straight 

 columella." The two latter characteristics are too vague to differentiate 

 a section, particularly in a group where modification of one or other of 

 these parts continually occurs, not only in one species as compared 

 with another, but in the separate species themselves. I, therefore, 

 hold with Ad. Schmidt, Boettger, Clessin, Kimakovicz, that no sub- 

 division of the group based on these grounds can be maintained. As 

 Clessin remarks (op. cit., p. 285), the general appearance of the 

 species not provided with an apparatus for closing the moutK bears 

 too close a resemblance to that of those which are so provided, added 

 to the fact that absolutely no anatomical difference exists between the 

 animals of the two sections, to make it possible to separate them 

 satisfactorily. 



Bcettger holds (ClausiUenstudien, p. 25) and I entirely agree with 

 him, that in Alopia we have, not a degenerate, but a survival of a 

 primitive form of Ciausilia, and that the abundance of Balea-like 

 fossil forms, and the rare occurrence of true lamellae in the then 

 existing clausilium-bearing Clausilias, make it more than probable 

 that all recent Clausilias are developed Baleas, and that this process 

 of development, from poorly armed to richly armed forms, is in 

 active working in the case of Alopia in the present day. 



Explanation of Plate. — Figs 1-4, Sections of the shell oi Alopia haueri {\), 

 glauca (2), livida (3), and deaniana (4), showing the gradual modification of the 

 columella for the reception of a clausilium. 



Figs. 5-8, the superior and inferior lamellse in the same four species. 



Fig. 9, Alopia deaniana n. sp. 



I In the case of livida some instability may be inferred from the fact that out of one 

 hundred full-grown specimens from the Bucsoiul, taken at random, in seven the lamella 

 superior was much under-developed, while in two it was scarcely discernible. Of fifty from 

 the Malajester Schlucht, three had no lamella superior. 



