510 Records of the Indian Museum. [Vol. VIII, 



Plectopylis (Chersaecia) bcdfordi, sp. n. 



(PI. xlii, figs. 2, 2a, 2&, 2c, 2d). 



Shell sinistral, depressed conoid, almost discoid, dark corne- 

 ouSj moderately umbilicated, finely and closely plicate-striate, 

 decussated on the upper side with very close raised spirals, giving 

 it a closely and finely reticulated appearance ; in addition there 

 are at more or less regular, distant intervals, coarser transverse 

 ribs ; at the sides the reticulated appearance is less distinct, and 

 there the shell is encircled by four distant fimbriae of cuticular 

 processes, resembling coarse hairs, and a similar fringe of cuticular 

 processes occurs at the top near the outer edge of the whorls ; 

 these processes are readily rubbed off. Whorls ()\, closely coiled, 

 increasing slowly and regularly, flattened above and at the side, 

 becoming convex towards the base, tumid below, the last not 

 dilated at the mouth, shortly and rather deeply deflexed in front, 

 angulated above. Spire depressed, suture linear, apex prominent. 

 Aperture oblique, auriculated ; peristome white, slightly thick- 

 ened and shortly reflexed, the margins approximating and united 

 by a raised flexuous ridge on the parietal wall, notched at the 

 junctions with the peristome above and below. 



The parietal armature consists of a simple curved transverse 

 plate, giving off posteriorly above a short support and rather 

 strongly deflexed backwards at its lower extremity, where it gives 

 oft' anteriorly a filiform fold running parallel with and close to the 

 lower suture and joining the flexuous ridges at the aperture. 

 The palatal armature is very complicated, being in two series ; 

 the anterior set consisting of six more or less horizontal folds ; 

 the first rather thin and short, parallel with and close to the 

 upper suture; the next four stouter and longer, the second slightly 

 curved, the third curving downwards in the middle and bifur- 

 cated at the posterior extremity ; the fourth at first curves upwards 

 and then downwards; the fifth similar to the fourth but, like the 

 third, bifurcate at the posterior extremity ; the sixth is parallel 

 with and near the lower suture. The posterior series consists of a 

 large number of more or less elongated denticles, all more or less 

 in a line with the posterior terminations of the folds ; three of these 

 between the first and second folds, the centre one shortest; one, 

 moderately long, between the second and third folds ; three be- 

 tween the third and fourth folds, the middle one longest; one 

 short one between the fourth and fifth folds ; two, the upper 

 one short and the lower one triangular, posteriorly to the fifth 

 fold ; two short ones between the last triangular denticle and the 

 sixth fold, with a short denticle anteriorly and close to the poste- 

 rior termination of the fifth fold ; and lastly a minute denticle 

 below the sixth fold. 



Major diam. 9, minor 8 mm. ; alt. 4*5 mm. 



Hab. — Abor country, Tsanspu Valley, on the Dihang, about 

 50 miles above the junction of the Sigon River, alt. 2800 ft. 



