5o6 Records of the Indian Museum. [Voi,. VIII, 



anteriorly from the upper extremity a thin horizontal fold, which 

 is provided below its anterior extremity with an elongate sinuous 

 denticle; 4°, a similar transverse concave fold with an anterior 

 horizontal fold, notched at the junction and curving upwards, the 

 denticle more distant from the anterior extremity ; 5°, a sinuous 

 transverse fold, its upper extremity deflexed posteriorly and its 

 lower extremity deflexed anteriorly, with a short horizontally elon- 

 gated denticle close to the lower extremity and provided on the 

 anterior side, in a line with its upper extremity, with an elongated 

 denticle, slightly curved downwards anteriorly, below the latter 

 occurs a short curved fold, its anterior end descending, and below 

 this again another horizontally elongated denticle in a line with 

 the denticle below the lower extremity of the transverse fold; 6°, 

 a slight sinuous horizontal fold close to the lower suture, its poste- 

 rior extremity slightly ascending. 



Major diam. I2'5, minor 11 mm.; alt, 5 mm. 



Hab.— Yamne Valley, Abor Hills and Sibbum (Oakes). 



Type No. 3125 Brit. Mus.; Nos. 6128 and 6130 Renging and 

 Rotung {Kemp) in Ind. Mns. 



This new species greatly resembles P. pinacis, but the last 

 whorl of the latter is more sloping towards the umbilicus and does 

 not descend in front, while the umbilicus is also more perspective. 

 In the armature considerable difference exists, more especially in 

 the palatal barriers, which are very complicated in the new 

 species. Five specimens, bleached and much worn, were collected. 

 A single specimen taken between Riu and Singging, on the Dihang 

 River, I refer to the same species. It is in much better condition 

 and is larger than the Yamne Valley shells, measuring 14-5 : 1275 : 

 5*5 mm. The species is named after Lieutenant G. F. T. Oakes, 

 the officer in charge of the Survey Party , who collected the shells. 



Plectopylis (Endothyra) gregorsoni, sp. n. 



(PI. xli, figs. 2, 2«, 26, 2C, 2d). 



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

 ous, polished below, widely and perspectively umbilicated, the 

 last quarter of the last whorl receding still further below, expos- 

 ing half the width of the penultimate whorl ; finely and regularly 

 ribbed, the ribs decussated by spiral ribs, giving the shell a 

 reticulated appearance on the upper side, the spirals being less 

 distinct at the side and disappearing at the periphery, below 

 which the transverse ribs also begin almost to disappear. Whorls 

 5, increasing slowly and regularly, flattened above, a little convex 

 at the side, steeply sloping towards the base, the last whorl 

 scarcely dilated at the mouth, very shortly and slightly deflexed 

 in front, angulated above, subangulated around the umbilicus, 

 the portion between the upper angulation and the periphery encir- 

 cled by three, about equidistant spirals. Spire depressed, suture 

 linear, apex a little raised. Aperture oblique, subhastate, peris- 

 tome white, thickened, and slightly reflexed; margins approximat- 



