PLECTOPYLIS. 



115 



The shell is solid, disc-shaped, measuring 24 to 26 millimetres 

 in diameter, of a light brown colour, with alternating streaks of 

 a lighter shade on the upper surface. It is composed of eight 

 M'horls, distinctly ribbed above and below, and very regularly 

 decussated above by raised spiral lines reaching as far as the apex 

 of the shell, the base is also spirally sculptured, but the sculpture 

 is less distinct ; the mouth of the shell is unarmed, but the parietal 

 callus forms a raised curved ridge which is distinctly free at both 

 ends from the peristome. The armature, which is comparatively 

 simple, occurs a little beyond the middle of the last whorl, and 

 consists of a simple strong vertical plate on the parietal wall (see 

 iig. 55 rt), giving off at its upper extremity a very small horizontal 

 tooth on the posterior side and a short horizontal lamella, 

 1-5 millimetres long, on the anterior side, while at its lower 

 extremity there is a slight callus on the posterior side. The 

 vertical parietal plate is shown sideways in fig. 55 h, where also 



Fig. 55. — Plectopylis andersoni. 



the palatal teetfa are seen as they appear from the posterior side. 

 Fig. 55 c gives the inside view of the outer wall, exhibiting the 

 palatal armature, which consists of four principal horizontal 

 lamellae terminating posteriorly in a triangular conical tooth ; 

 above these are ; first a minute tooth, aud secondly, higher up, a 

 small fold near the suture, while at the base of the palatal wall are 

 also : first a minute tooth, and secondly, nearer the suture, a small 

 fold. The specimen figured is in Mr. Ponsonby's collection. 



III. Section Endoplon, Gude. 



Endoplon, Gude, Science Gossip, n. s. vi, 1899, p. 148. 



Dextral. Palatal folds horizontal, oblique, or almost vertical. 

 Type, Helix (Plecfop)jUs) hradujplecta, Benson. 

 Range. Burma, Tonkin. 



103. Plectopylis smithiana, Oude. 



Plectopylis smithiana, Gude, Science Gossip, N. s. iii, 1897 



tig. 38 (shell and armature). 

 Plectopylis {Endoplon) smithiana, Gude, op. cit. vi, 1899, p. 



I 2 



r4, 



148. 



