POLYGYRA. 155 



very strongly and suddenly constricted behind the lip, which is 

 reflexed, thickened and white ; the outer and outer-basal segment of 

 the lip is strongly thickened, and at the middle of the outer lip there is 

 a hardly noticeable tubercle, with another a little outside of the middle 

 of the basal lip, the space between them more thickened inwardly ; 

 parietal wall bearing an oblique, curved blade-like tooth. 

 Alt, 6-8, diam. 11' 7 mill. 



Boston Mts., Crawford Co., Arkansas. 



Triodopsis edentata SAMP., Nautilus iii, p. 85, figs. (Dec., 1889.) 

 The form and sculpture are quite as in H. inflecta, but the obsoles- 

 cence of the lip-teeth render it strikingly different from that species. 



METODONTIA (Vol. Ill, p. 149.) 



This section must be removed to the neighborhood of section 

 Petasia. It has nothing to do with Triodopsis. 



MESODON (Vol. Ill, p. 150.) 



H. ARMIGERA Ancey. PI. 50, figs. 21, 22, 23. 



Shell perforated, globose, rather thin but solid, light chestnut- 

 brown ; entire surface (except inner 2 } whorls) clothed with delicate 

 short equidistant hairs, arranged in very oblique rows. 



Spire low-conoid, apex obtuse. AVhorls of, convex, slowly widen- 

 ing, last whorl rounded, very convex below, very little deflexed in 

 front, decidedly contracted behind the lip, which is regularly and 

 rather widely expanded, dilated at the columellar insertion, its face 

 brown. Parietal wall often having a small lamellar white tooth. 

 Aperture rotund-lunate, somewhat oblique. 



Alt. 8, diam. 12 mill. 



San Francisco, California, to Vernon, B. C~ 



This is smaller than the typical H. columbiana, more globose and 

 convex beneath, more densely hirsute, and with less expanded per- 

 istome. 



H. KIOWAENSIS Simpson. PI. 50, figs. 13, 14, 15. , 



Shell depressed, umbilicated (the umbilicus deep, and one-tenth 

 the diameter of the shell), solid, opaque, straw-colored, minutely 

 speckled with buff. Surface somewhat shining, regularly striated 

 obliquely, and showing under a lens traces of microscopic spiral 

 lines. Suture moderately impressed. Spire convex. AVhorls 5-5&, 

 slowly widening, the last slightly falling at the aperture, quite con- 



