1884.] OF THE 'CHALLENGER ' EXPEDITION. 2/9 



the total length. The peristome is thin, narrowly reflexed on the 

 lei't of the aperture, and rather broadly expanded in the umbilical 

 region, and has the extremities, which converge but very slightly, 

 connected by a thin callus spread over the whorl. 



Length 8 millimetres ; diameter 3| ; length of- aperture 2\, 

 width 2. 



5. Balea (Tristania) tristensis, Gray. 



Balea tristensis (Leach, MSS.), Gray, Zool. Journ. vol. i. p. CI, 

 pi. vi. fig. A. 



Hab. Tristan d'Acunha, October 15, 1873. 



This species is more slender and longer than B. ventricosa, 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. 



South America. 



The few species collected on the mainland and adjacent islands 

 are for the most part well known. It is curious to note that Limax 

 gar/ates, which I have already recorded among the 'Challenger' 

 collections from Bermuda, Tristan d'Acunha, and South Africa, 

 is again found at the island of Juan Fernandez. On placing side 

 by side the specimens from these four localities, I am unable to 

 trace any external difference. 



The species are the following : — 



1. H. (Stepsanoda) quadrata, Ferussac. 



Hab. Juan Fernandez island. 



All the specimens brought home by the 'Challenger' differ 

 slightly from those in Cuming's collection identified by Dr. Pfeiffer 

 as belonging to this species. They are a little more depressed, just 

 a trifle more widely umbilicated, and have a somewhat smaller 

 aperture. 



2. Helix (Stepsanoda) selkirki. (Plate XXIII. figs. 19-195.) 

 Shell small, discoidal, deeply umbilicated, thin, pale, spotted above 



with red, irregularly streaked beneath with a lighter tint. "Whorls 

 6-7, very narrow, tightly coiled, slowly increasing, convex, narrowly 

 channelled at the suture, sculptured with close-set, hair-like lines of 

 growth ; last whorl a little spreading towards the aperture, where it 

 exhibits a very faint depression or constriction near but a little above 

 the middle ; spire flattened, only the least raised above the body- 

 whorl. Aperture oblique, irregularly lunate ; peristome simple, 

 thin. Diam. 4 milliut. ; height 2. 



Hab. Island of Juan Fernandez. 



This species is of the same size and general appearance as H. 

 esse/lata, Muhlfeldt, from the same locality, and probably exists in 

 ollections intermingled with that form. It is, however, distin- 



