AUSTRALIAN LAND SHELLS. 13 



A shell easily recognised, although it varies much in markings, 

 and is sometimes without any, and entirely of a light brown. 

 Usually the ribs are black at intervals, or wholly, giving the shell a 

 streaked appearance. 



29. Helix inusta. Cox. Plate X. Fig. 3, natural sue and mag- 

 nified. M.C. 



Helix nautiloides. Cox. 



Cox, Pro. Zool. Soc, 1865, p. 696. 



Shell perforated, orbicularly depressed, discoid, regularly finely ribbed 

 in an arcuately curved manner, covered with a reddish-horny epi- 

 dermis, not shining ; spire flat, suture impressed ; whorls 4, convex, 

 the last rounded and rather tumid, above towards the suture convex, 

 slightly flattened towards the mouth, not descending ; aperture 

 nearly diagonal, obliquely ovately -lunate, pearly within ; peristome 

 simple, sinuated above, at first horizontal, then sloping downwards, 

 and curved to the columella, which is slightly expanded above, and 

 partially concealing the small umbilicus. 



Diameter, greatest - 23 ; least 0'19 ; height 0"12 of an inch. 



Habitat. Clarence and Richmond Rivers. MacGillivray. 



A dull reddish-brown shell, closely allied to H. sericatula, but a 

 smaller, more delicate, and a more finely ribbed species. A pale 

 variety from the Clyde River has 5 whorls, and some small dark 

 specimens from Greystane's, Parramatta, almost inosculate with the 

 preceding species. 



30. Helix cochlidium. Cox. Plate VIII. Pig 1, natural size 

 and magnified. M.C. 

 Cox, Pro. Zool. Soc., 1867. 



Shell umbilicated, depressed, sub-discoid, thin, translucent, glassy, not 

 shining, with numerous prominent, thin, elevated, pbcate ribs, 

 regular, arcuately curved, the interstices under the lens very minutely 

 granulated and linearly streaked, white; spire flat, suture moderate; 

 whorls 4, convex, the last narrow, rounded, rather flattened from 

 without, not descending in front, but rather inflated below ; below 

 plicately ribbed as above, outer margin of umbilicus steep, and not 

 gradually merging into the base ; umbilicus wide, only slightly 

 narrower at the bottom; aperture oblique, lunate, higher than 

 broad; peristome simple, frequently when formed by one of the 

 plicate ribs appearing as if expanded. 



Diameter, greatest 0-09 ; least 0-08 ; height 0-04 of an inch. 



Habitat. Clarence River, under logs with PL. iuloidea. MacGillivray. 



Closely allied to the next species, but comparatively with it, strongly, 

 and even coarsely sculptured. Named from the staircase like appear- 

 ance of the umbilicus. 



31. Helix pexa. Cox. Plate VIII. Pig. 2, natural size and 

 magnified. M.C. 



Shell umbilicated, depressed, discoid, thin, transparent, not shining, 

 very regularly and closely arcuately costate, each costa generally 



