60 HELIX. 



last descending, base decussated by more or less obsolete lines ; 

 aperture with two somewhat acute parietal lamellae. 



Diam. 5'75 mill. 



Sandwich Islands. 

 H. setigera, Gould, is a synonym. 



H. DECUSSATULA, H. PAUCicosTATA ( H. filocostata, Pse., is a syno- 

 nym), H. DISTANS, Pease. (Unfigured.) Sandwich Islands. 



H. UNILAMELLATA, Garrett. PL 11, figs. 74-76. 



Widely umbilicated, thin, corneous, tessellated and rayed with 

 chestnut, obliquely, compressly, closely plicately ribbed, ribs 

 finer and closer below ; whorls 5, convex, slowly, regularly 

 increasing; the last not descending in front, obtusely subangular 

 on the periphery, more distinctly so around the umbilicus, suture 

 channeled ; parietal region with a single small lamella. 



Diam. 4-5 mill. 



Rarotonga, Cook's Is. 

 H. ROTELLTNA, Pease. PI. 11, figs. 82, 83. 



Narrowly umbilicated, thinVy, radiate^, elevately striated, 

 rather thin; whorls 5, convex, the last rounded; parietal wall 

 with a sino-le entering lamella ; color alternate strigations of 



O O ' O 



chestnut and yellowish. Diam. 2 mill. 



In s. Aitutake. 

 H. coNsiMiLis, Pease. PL 11, figs. 80, 81. 



Widely umbilicated, rather thin, closely radiate^ costellate, 

 tessellated with chestnut and vellow above, strigate with chestnut 



/ 



below; whorls 5, convex, suture impressed, periphery rounded ; 

 parietal wall with a single lamella. Diam. 4 mill. 



Tahiti, Eaiatea. 

 H. ACUTICOSTA, Mousson. PL 11, figs. 60, 61. 



Widely umbilicated, closely arcuately ribbed-striate, corneous, 

 with chestnut tessellations, suture deep ; whorls 5, convex, slowly 

 increasing, turgid next the suture, last whorl slightly depressed 

 above, not descending, base convex ; parietal wall with one, two 

 or verj- rarely three lamella?. Diam. 4'3 mill. 



Raiatea, Society Islands. 



Larger and more depressed than H. consimilis, the umbilicus 

 larger and ribs finer. A uniform whitish horn-colored variety 

 occurs. 



