2/8 MR. E. A. SMITH ON THE MOLLUSCA [May 6, 



Tristan d'Acunha. 



Until now the known land-inollusks from these islands consisted 

 of the two species of Balea mentioned below. The discovery there- 

 fore of three additional terrestrial forms is particularly interesting, 

 two of them, however, being also found elsewhere. The species 

 are : — 



1. LiMAX CANARiENSis, d'Orbigny. 



Several specimens from the above locality agree in all external 

 characters with those from Teneriffe which I have identified with 

 this species. As a rule they are reticulated and mottled on the back 

 with black, but in one or two instances this colouring is almost entirely 

 absent. 



2. LiMAX gagates, Draparnaud. 



A single specimen, in contraction three quarters of an inch in 

 length, appears to agree externally in every respect with this well- 

 known European form. It has also been recorded from the Azores, 

 Madeira, St. Helena. 



3. Helix (Hyalinia) exulata. (Plate XXIII. figs. 18, 18 J.) 



Shell depressed, orbicular, thin, moderately widely and deeply 

 umbiHcated, seniitransparent, pale yellowish horn-colour, glossy, 

 Sf^ulptured with oblique curved lines of growth. Whorls 5, convex 

 above, distinctly margined below the suture, rather rapidly enlarging, 

 the last not descending in front. Spire very depressed, only a little 

 raised above the body-whorl, terminating at the apex in a large 

 nuclear volution which is scarcely at all elevated above the succeeding 

 one. Aperture broadly lunate, slightly oblique ; |)eristome thin, a 

 very little thickened and expanded on the columellar side. 



Greatest diameter 7| niilhm., smallest 6|, height 4. 



Hah. Tristan d'Acunha. 



Although several species from various parts of the world bear 

 considerable resemblance to this little unpretending form, still none 

 are apparently identical. 



4. Balea (Tristania) ventricosa. Gray. 



Balea ventricosa (Leach MSS.), Gray, Zool. Journ. vol. i. p. 62, 

 pi. vi. fig. B. 



Hab. Inaccessible Island, Tristan d'Acunha, October 16, 18/3. 



This species has not, as far as I can ascertain, ever been fully 

 characterized, the diagnosis of Gray, consisting of five words only, 

 being totally inadequate. 



It may be described as pupiform, pale olive-brown, narrowly rimate, 

 sculptured with rather strong oblique lines of growth. The whorls 

 are six and a half to seven in number, rather rapidly enlarging, convex, 

 divided by a deep oblique suture. The spire has curved outlines, 

 and terminates above in an obtuse rounded smooth apex. The 

 aperture is rather large, and occupies somewhat less than a third of 



