Mollusca.] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 35 



Genus Therasia, Hutton, 1883. 

 Distribution. — New Zealand only. 



Therasia (?) antipoda (Hombron and Jacquinot), 1854. 



Hdix antipoda, Hombron and Jacquinot, Voy. P. Sud., v, p. 18, pi. vi, figs. 13-16. 

 Charopa (Thalassia) zdandiae antipoda, Man. Conch. (2), ii, p. 214, 

 pi. Ixiii, figs. 65-67. Hdix aucklandica, Le Guillou, Rev. Zool. v, 1842, 

 p. 140 ; Hutton, M.N.Z.M., p. 19. 



An emended diagnosis, derived to some extent from specimens collected by 

 Professor Benham, is here offered. 



Shell small, orbicularly conoidal, umbilicated, striated, shining, thin and semi- 

 transparent, periphery keeled. Sculpture : protoconch indistinctly microscopically 

 striate, the following whorls with inequidistant and very unequal oblique radial 

 striae and plaits, the interstices minutely reticulated by growth and spiral striation, 

 the radial sculpture less prominent over the base. Colour yellowish-brown, with 

 radial unequal streaks of rufous. Epidermis very thin and shining. Spire broadly 

 conoidal, of about the same height as the aperture. Protoconch of 1| smooth and 

 flatly convex volutions. Whorls 5| to 6, regularly increasing, flattish, the last 

 sharply keeled ; base convex. Suture much impressed. Aperture broadly sub- 

 quadrangular. Peristome acute, simple, very thin ; outer lip descending almost 

 straight, angled on meeting the slightly convex basal lip. Columella oblique, concave, 

 slightly reflexed. Umbilicus moderate, somewhat perspective, deep. 



Diameter, 7 mm. ; height, 4 mm. Type. 



Jaw arcuate, composed of numerous vertical plaits. Only a very young speci- 

 men was at my disposal for preparing the radula, and the teeth were so small that 

 even a magnifpng- power of 720 did not show their character very clearly. All 

 teeth of a transverse row seemed to be alike, narrow and elongated, with 2 minute 

 cusps. This leads one to assume that in this species at least the differentiation of 

 the teeth takes place at a later period of growth. 



Hfjh. — Auckland Islands, under logs (Professor Benham). 



This is the first time I have seen this species, and I have now come to the con- 

 clusion that Hdix aucklandica, Le Guillou, and Helix antipoda, H. and J., are identical. 

 As Le Guillou gave no figure of his species, I give validity to the name bestowed 

 on the shell by Hombron and Jacquinot. 



This species is somewhat alUed to Therasia traversi, E. A. Smith, which, how- 

 ever, is a larger shell, has no radial plaits, and a much narrower umbilicus. The 

 dentition being still unknown, it is uncertain whether the species belongs to Therasia 

 or Thalassohdis ; for the present I class it under the former genus. 



The Thalassohdix zdandiae antipoda of Hutton, from the South Isknd of New 

 Zealand, has nothing to do with the species of Hombr. and Jacq. ; it is simply a 

 variety of T. zdandiae, Gray, in which the brown radial bands extend over the base. 



Genus Phenacohelix, Suter, 1892. 

 Distribution. — New Zealand only. 



