86 



HBLICID^. 



84. Plectopylis pinacis, Benson. 



Helix pinacis, Benson, A. M. N. H, ser. 3, iii, 1859, p. 268 ; Hanley 

 & Theobald, Conch. Ind. 1870, pi. 13, fig. 5; 1874, pi. 84, 

 figs. 1, 4. 



xliv, 1875, pi. 7, tig. 2 (shell and animal). 

 Helix (Atopa (Plectopylis)) pinacis, Tryon, Man. Conch, ser. 2, iii. 



1887, p. 159, pi. 34, figs. 53-55. 

 Plectopylis pinacis, Pilsbry, Man. Conch, ser. 2, ix, 1894, p. 146 ; 



Gude, Science Gossip, N. s. iii, 1897, p. 206, fig. 32 (shell and 



armature) ; Godwin-Austen, Moll. India, ii, 1907, p. 203, pi. 114, 



fig. 2 (anatomy). 

 Plectopylis (Endothyra) pinacis, Gude, Science Gossip, N. s. vi, 1899, 



p. 148. 



Helix (Gorilla) pettos, Martens, Malak. Blatt. xv, 1868, p. 158. 

 Helix pettos, Pfeiffer, Novit. Conch, ser. 1, iii, 1869, p. 462, pi. 101, 



figs. 7-9. 



Original description : " Testa sinistrorsa, late umbilicata, orbi- 

 culato-depressa, superne oblique scabre plicato-striata, liris con- 

 fertis spiralibus, subtus striis obliquis flexuosis striisque spiralibus 

 decussata, cornea, epidermide fusca, scabra (junioris ad carinam 

 praesertim hispida) induta ; spira planata, vix elevatiuscula, apice 

 planato, sutura leviter impressa ; anfractibus 7| planulatis, lente 

 et arete accrescentibus, ultimo antice breviter descendenle, superne 

 subcarinato, subtus valde convexo, circa umbilicum profundum, 

 perspectivum, conicum, compressiusculo ; apertura valde obliqua, 

 lunari, peristomate expansiusculo, reflexo, albiclo, marginibus callo 

 brevi, laminari, elevatiusculo, sinuato junctis. 



*' Diam. maj. 14, min. 12^, axis 4J mill." (Benson.) 



Hob. Sikkim : Darjeeling (Blanford, Stoliczka, Mainwaring) 

 Eungun, Pankabari (Blanford) ; Bungmaval (Blanford) 

 Damsang (Godwin- Austen). 



Nevill was the first to suspect that Helix (Gorilla} pettos was 

 identical with Plectopylis pinacis. The type of the former, which 

 is in the " Kb'nigliche Museum tiir Naturkunde," Berlin, was 

 forwarded to me for inspection in 1897 by the late Dr. von 

 Martens, with permission to open the shell for the purpose of 

 examining its armature, which enabled me to satisfy myself that 

 the two species were in fact identical, both as regards armature 

 and shell characters. 



The parietal armature (fig. 35 c] consists of a single strong 

 vertical plate, which is strongly abruptly deflected anteriorly 

 at the lower extremity, and gives off posteriorly a club-shaped 

 support ; the upper extremity gives off two slight supports, one 

 on either side, the posterior one horizontal, and the anterior 

 one a little lower, oblique, and very short; a little below the 

 posterior support occurs a small denticle ; a free, thin horizontal 

 fold is found below the vertical plate ; see also fig. 35 a, which 



