GASTEROPODA. Be 
Diameter one-tenth of an inch; axis one-twentieth of an inch. 
Common under stones at Aurora or Metia Island; also at Tahiti. 
In size and colour this resembles H. contorta, Fer., but the spire is 
more depressed, the whorls are more numerous and more compactly 
wound; there are twice as many lamell on the penultimate whorl, 
and the aperture is more contracted. From H. bursatella it differs in 
the aperture, the teeth, and in wanting a carina. The umbilicus is 
similar in form to that of the young H. bursatella, but the whorls, in 
forming it, maintain their rounded shape, instead of being flattened. 
It is smaller than the next species. 
Figures 51, 51 a, 51 4, three views of the shell, enlarged; 51 c, na- 
tural size; 51d, the aperture, magnified. 
Hewix nystrix (Mighels ). 
Testa parva, discoidea, late umbihcata, tenuis, fusco et luteo tessellata : 
sptra planulata, ad apicem indentata ; anfractibus quinis, clathris 
creberrimis setigerts, aliquando denudatis, insignibus : apertura lunata, 
lamellis duobus conspicuis intro volventibus instructa. 
Helix setigera, Goutp; Proceed. Boston Soc. Nat. Hist., i. 174. 
May, 1844. 
Helix hystrix, MicHEts, in sched. ; PFEIFFER, Symb., 1. 67; Monog. 
Helic. Viv., i. 116; Curemn., 2d edit., No. 560, tab. 89, f. 8-11. 
SHELL small, planorboid, thin, checked above with radiating stripes 
of dusky and golden yellow, in about equal proportions, and becoming 
flexuous or zigzag as they pass to the under side. Spire flat, with the 
apex even depressed ; whorls five, ornamented with numerous rib-strie 
which radiate from the apex, and which, when fresh, are garnished 
with long crisped black hairs, that are easily rubbed off. Beneath, 
the whorls are more rounded than above, and there is a deep, broad 
umbilicus, about one-third the width of the base. Aperture lunate, 
lip simple, and within the throat two well-developed lamelle usually 
revolve. 
