PLECTOPYLIS. 81 



fold, which is absent in P. sowerbyi, where the plate in question 

 is only provided with a support anteriorly and a denticle pos- 

 teriorly below, and there is no horizontal fold below it ; so that 

 in this respect the present species differs from both its allies (see 

 fig. 30/, which shows part of the parietal wall with its armature). 

 The palatal armature is in one series, and consists of six horizontal 

 folds. The first fold is very short and slight ; the second longest ; 

 the third, fourth, and fifth each a little shorter than its prede- 

 cessor ; the sixth slight and very short (see fig. 30 e, which shows 

 the inside of the outer wall with its folds). All the figures are 

 enlarged. 



82. Plectopylis plectostoma, Benson. 



Helix plectostoma, Benson, J. A. S. B. v, 1836, p. 351 ; Reeve, 

 Conch. Icon, vii, 1852, pi. 129, fig. 782 ; Pfeiffer, Conch.-Cab., 

 Heliceen, i, 1846, p. 367, pi. 64, figs. 19-21 ; Nevill, Hand List, 

 1878, i, p. 71 ; Hanley & Theobald, Conch. Ind. 1870, pi. 13, 

 fig. 2. 



Helix (Plectopylis} plectostoma, Benson, A. M. N. H. ser. 3, v, I860, 

 p. 247 ; Blanford, J. A. S. B. xxxiv, 1865, p. 194 ; Godwin- 

 Austen, P. Z. S. 1874, p. 612, pi. 73, fig. 2 (armature). 



Helix (Atopa (Plectopi/lis) ) plectostoma, Tryon, Man. Conch, ser. 2, 

 iii, 1887, p. 160, pi. 34. figs. 69, 70. 



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

 p. 274, fig. 39. 



Plectopylis (Endothyra) plectostoma, Gude, op. cit. vi, 1899, p. 148. 



Original description : " T. reversa, depresso-conoidea, subtus 

 tumida; spira exsertiuscula ; anfr. 5 supra planati, radiatim plicati, 

 rugis transversis decussati, ultimus angulatus : angulo subtus 

 marginato ; apertura lunata, plica (ut in H. personata) interdum 

 inconspicua, ultimo anfractui adhserente ; umbilicus prof undus, 

 anfractus plerosque exhibens." (Benson.) 



Diam. maj. 9, min. 8 ; alt. 4*5 mm. 



Bab. India: Naga Hills (Chennell); Dana Hills, Khasi Hills 

 (Godwin- Austen). Burma : Arakan Hills (Kurz) ; Tongoop 

 (Ingram) ; Bassein, Pegu (Blanford) ; Sylhet (Nevill). Sikkim : 

 Darjeeling (Blanford, Stoliczka, Mainwaring). 



A careful scrutiny of a number of shells in various collections 

 revealed the fact that two different forms, one with and one 

 without a horizontal fold given off from the parietal vertical plate, 

 have been included under P. plectostoma, and it became therefore 

 necessary to decide which of the two conformed to Benson's type 

 in the Museum of Zoology at Cambridge. In 1897, through the 

 kindness of Dr. S. E. Harmer, then in charge of the Museum, I 

 was able to examine the type specimens, one of which I figured in 

 ' Science Gossip,' and which is now reproduced. Although 

 Benson's reference to the armature in his amended description 

 (1860), " lamina 1 parietal! verticali, simplici, lamellis nullis 

 munita," inclined me to conjecture that the form without the 



