PERIDERIOPSIS. 245 



mella conspicuously arcuate-twisted, bluish-brown. Length 

 40-54, diam. 15-18.5 mm.; apert. 15-18 mm. long (D. et P.). 



Congo Free State: Stanley Falls, in the forest (P. Dupuis). 



Perideriopsis fallsensis D. et P., Bull, des seances de la 

 Soc. Roy. Malac. Belgique, Mar. 3, 1900, p. xiii, figs. 19, 20; 

 in Ann. Soc. Roy. Malac. Belg., xxxv. 



4. P. MVULAENSIS Dupuis et Putzeys. PI. 17, figs. 78, 79. 



Shell narrowly perforate, rather solid, subpyramidal- 

 turriculate, a little shining; apex obtuse; whorls 8, a little 

 convex, frequently minutely depressed or sloping at the 

 suture, sometimes flattened, suture moderately crenulate and 

 sometimes margined; upper whorls granulose, two or three 

 following ones very delicately granulate, all the follow- 

 ing striatulate with growth-lines. Surface diversely varie- 

 gated, sometimes yellowish with brown forked flames, wider 

 above the suture, sometimes brown, beautifully tessellate- 

 flamed below the suture with white. Last whorl subangular, 

 with varied basal coloration. Aperture subtrapezoidal, the 

 lip a little reflexed, twisted, extending nearly to the base, 

 and forming an angle with the lip margin; columellar mar- 

 gin reflexed, parietal callous variable. Length 38-51, diam. 

 17-21 mm.; length aperture 14-18.5 mm. (D. et P.). 



Congo Free State: Is. of Mvula (P. Dupuis). 



P. mvulaensis D. et P., Bull, des seances, etc., Mar. 3, 1900, 

 p. xiv, f. 21, 22. 



This species is readily distinguished from P. fallsensis. It 

 is less glossy than the latter, the shell especially is thinner, 

 the ground-color yellowish or even entirely brown, the form 

 more regularly pyramidal, the base wider, the aperture more 

 trapezoidal, and the lip a little reflexed and noticeably thick- 

 ened at the edge, while in P. fallsensis the thickening is de- 

 veloped as an internal labial deposit. Moreover, except in 

 the entirely brown examples, all the specimens of P. mvu- 

 laensis which we have are ornamented at the edge of the 

 angle of the last whorl with a well-marked brown band, 

 which we have not observed in any specimen of the other 

 species (D. et P.). 



