1887.] MOLLUSKS ON THE VITI ISLANDS. 169 



It may at once be recognized by its large size (38 millim. in 

 diameter), depressed turbinate form, yellowish or light brownish 

 horn-colour with a wide fulvous-brown sutural band. 



11. Nanina assavaensis, n. sp. 



Shell imperforate, turbinately globose, indistinctly striated with 

 rather coarse lines of growth, smooth, shining, subpellucid, smoky 

 horn-colour ; whorls 5, slightly convex, the last one obscurely 

 angulated just above the periphery ; aperture oblique, orbicular- 

 luniform ; peristome thin, straight ; columella abbreviately reflected 

 over the axis of the shell. 



Diam. 20, height 12 millim. 



Abundant beneath dead leaves at Naviti Island, one of the Assawa 

 group. 



Genus Microcystis, Beck. 



1. Microcystis unisulcata. 



Nanina unisulcata, Mousson, Journ. de Conch. 1865, p. 191; 

 {Microcystis) 1870, p. 113; (Thalussina) Paetel, Cat. Conch. 1873, 

 p. 85 ; Schmeltz, Cat. Mus. Godeff. v. p. 90. 



Helix unisulcata, Pfeiffer, Mon. Hel. v. p. 80. 



Helix (Petasia) unisulcata, Paetel, Cat. Conch, p. 96. 



Helix laqueata, Baird, Brenchley, Cruise of the ' Curagoa,' p. 446, 

 pi. xl. figs. 8, 9. 



This peculiar species is widely diffused throughout the group, and, 

 like all the Yiti species, is found beneath decaying vegetation. 



It is the only species, so far as known, which exhibits a sculptured 

 surface. The unisulcated whorls and more or less nodulous columella 

 will readily distinguish it. 



2. Microcystis kioaensis. 



Nanina kioaensis, Garrett, Proc. Phil. Acad. Nat. Sci. 1873, 

 p. 237, pi. 3. fig. 71 (" kifaensis " in error). ^/ 



Naninal taviuniensis, Liardet, Proc. Zool. Soc. 1876, p. 99, pi. 5. I 



figs. 1, la, b. 



This very distinct species only occurred to my notice in the 

 mountain-forests of Kioa Island. Mr. Liardet's Nanina taviuniensis, 

 which he obtained at Taviuni and Gomen, differs only from our 

 species in having the base minutely perforated. 



It may be distinguished by its depressed globose form, yellowish 

 horn-colour, deep rounded body-whorl, and the prominent columellar 

 fold. 



3. Microcystis nodxjlata. 



Nanina (Microcystis) nodulata, Mousson, Journ. de Conch. 18/0, 

 p. 1 14, pi. 7. fig. 4 ; (Thalassia) Paetel, Cat. Conch, ed. 1873, p. H5. 



Helix nodulata, Pfeiffer, Mon. Hel. vii. p. 67. 



Discovered by Dr. Graffe on Vanua Balavo, one of the Windward 

 Islands. 



Its chief characters are its depressed globose form, brilliant horn- 



