GUDE : ON THE ARMATUKB OF LAND BIOLLUSCA. 67 



but the upper lip here has a strong nodule, the basal lip bears on its 

 outer portion two strong, entering lamellae on a common base, and 

 nearer the columella a strong, entering lamella and two denticles, 

 all on a common base, a deep sinus occurring between these two 

 sets, and all having corresponding scrobiculations. P. clappi, Pils., 

 from Columbia, has the peristome developed to an unusual degree ; 

 its parietal callus and lamina resemble those in the last-mentioned 

 species, but there is only one lamella on the outer part of the basal 

 lip, and neareT the columellar there are two parallel, entering lamellae, 

 while the upper lip also has an entering lamella ; all these folds or 

 lamellse are unusually well-developed and strong, especially those 

 near the columella. 



The next section, Thelidomus, Swainson, is not remarkable for its 

 teeth or lamellae, these being, generally speaking, conspicuous by 

 their absence, but the section Polydontes, Montf. — consisting of but 

 three species confined to Cuba — has one very remarkable member, 

 P. imperator, Montf., which has an unusually strong and thick 

 peristome, its inner edge being provided with a series of very strong 

 teeth over its entire length and an obtuse fold near the columella. 



Genus Aulacospira, von MoellendorfE. 



Some seven species, all minute, are known, occurring in the 

 Philippine Islands. Most of the species have four or five teeth in 

 the aperture, one being provided with only one, A. hololoma, Mlldfi., 

 and one being edentulous, A. mucronata, Mlldff. A. azpeitice, Hid., 

 has a long oblique pliciform tooth on the parietal wall, one transverse 

 on the columella, and three smaller ones on the basal and outer 

 margins. 



Genus Metodonta, MUdff. 



A small genus comprising four known species from northern 

 China, with lunate aperture nearly closed by two large teeth situate 

 on a transverse callous ridge on the basal and outer walls a short 

 distance from the edge of the peristome, and meeting two somewhat 

 small teeth on the parietal callus, also on a common base, and with 

 a small denticle on the columella. Examples : M. houaiensis, Cr., 

 and M. moltneri, Gredl. 



Genus Helicodonta, Ferussac. 

 This group of European, north African, and south-east Asiatic 

 distribution is characterized by a discoid form, or nearly so, of 

 shell, the aperture being mostly triangular, lunar, rhomboid, with 

 frequently teeth on the margins of the peristome. The section 

 Loosia, Hesse, was established for the reception of one species, 

 H. diodonta, Fer., from Hungary, a small flattened shell, with sub- 

 triangular aperture, the upper margin being furnished with a short, 

 strong, obtuse tooth, while the lower margin carries a very stout, 

 broad fold, which is continued within for about one-third of a whorl 



