TRISTANIA. 21T 



Genus TRISTANIA Boettger. 



Tristania BTTG., Systematisches Verzei-chniss der lebenden 

 Arten der Lands<chnecken-Gattung Clausilia Drap, in 17r. und 

 18r. Bericht Offenbacher Vereins fiir Naturkunde, 1878, p. 

 19. Not Tristania Kirby, 1892. 



Shell sinistral, perforate, oblong-turrite, pale brown, com- 

 posed of Qi/2 to 8^/2 convex whorls ; apex obtuse, smooth and 

 rounded. Aperture ovate, peris/tome simple, thin, the colu- 

 mellar margin well expanded, parietal callus thin. 



Soft anatomy unknown. Type T. tristensis. 



The reference of this group to the Palaearctic genus Balea 

 was evidently due to its turrite shape and sinistral coil. 

 Its rank and position are uncertain, pending information on 

 the soft anatomy, but a place near Opeas seems indicated by 

 the characters now known. No sinistral Opeas has been 

 described, but throughout the Achatinidce there are occa- 

 sional sinistral species or groups among the dextral forms. 



Neither species has been adequately illustrated. Boettger 

 had apparently not seen them. He gave no diagnosis of 

 Tristania. 



1. T. TRISTENSIS (Gray). PI. 40, fig. 10. 



Shell subulate-ovate, reddish-brown, axis .4, diam. .1 of 

 an inch (Gray). 



"This species is more slender and longer than B. ventri- 

 cosa, and has one and at times two additional whorls, which 

 are more convex and more slowly enlarging. The characters 

 of the sculpture, of the umbilicus, and aperture are very 

 alike in both forms, the latter of course being shorter in 

 proportion to the total length of the shell/ 7 (E. A. Smith). 



Tristan d'Acunha (Capt. Carmdchael; Challenger). 



Balea tristensis Leach Mss., GRAY, Zoological Journal i, 

 p. 62-63, pi. 6, f. A (1825). PFR., Monogr. ii, p. 388. Pupa 

 tristensis GRAY, Ann. of Philos. 1825, ix, p. 413. Balea 

 (Tristania) t., SMITH, P. Z. S. 1884, p. 279. 



2. T. VENTRICOSA (Gray). PL 40, fig. 11. 



Shell lanceolate-ovate, pale brown, axis .3, diam. .1 of an 

 inch (Gray). 



