Tethys.] GASTROPODA. 545 



KEY TO SPECIES. 



A. Shell ear-shaped, with irregular radial plications and fine lines ; 



right side lightly convex, left upper margin broad and excavated brunnea. 



B. Shell elongated, with concentric growth-lines only ; right side 



auriculated, left upper margin obliquely descending, lightly 

 concave . . . . . . . . . . . . Tryoni. 



0. Shell subquadrangular ; embryonic shell concentrically coarsely 



striated, the remainder smooth, polished ; right side somewhat 

 auriculated, left upper margin convex . . . . . . venosa. 



1. Tethys brunnea, Button, 1875. Plate 23, fig. 11. 



Aplysia brunnea, Hutt., T.N.Z.I., vii, 1874 (1875), 279, pi. 21 ; J. de Conch., 

 1878, 41 ; M.N.Z.M., 123. Tethys brunnea, Hutt., Man. Conch. (1), xvi, 

 97, pi. 59, f. 44 ; Index, 68. Aplysia Hamiltoni, T. W. Kirk, T.N.Z.I., 

 xiv, 1881 (1882), 283. Tethys Hamiltoni, Kirk, Man. Conch. (1), xvi, 99 ; 

 Index, 69. 



Shell horny, ear-shaped, moderately convex, membranous, with a 

 thin inner calcareous layer. Sculpture consisting of numerous well- 

 marked concentric growth-lines, crossed by irregularly spaced radiate 

 plications and fine lines. Epidermis extending beyond the, calcareous 

 layer, thin, straw-colour or pale brown, polished ; inside white, with 

 a pearly lustre. Apex much recurved, tubercular. Right side of shell 

 lightly convex, base broadly rounded, left side but little rounded, 

 upper margin broad and excavated. 



Diameter, 18 mm. ; height, 23 mm. (type). Diameter, 32 mm. ; 

 height, 43 mm. (type of T. Hamiltoni). 



Animal umber-brown, with fine irregular dark markings ; lighter 

 below. Length about 100 mm. (type) ; or 180 mm. long and 65 mm. 

 broad (type of T. Hamiltoni). 



Type in the Dominion Museum, Wellington. 



Hob. Wellington (type) ; Dunedin ; Petane, near Napier (A. 

 Hamilton), type of T. Hamiltoni. 



Remarks. The type is broken, but sufficient is left to show that 

 the outlines of Mutton's drawings are correct. The type of T. Hamil- 

 toni is inseparable from T. brunnea, but it is larger, and seems to 

 represent the adult form. As pointed out by Captain Mutton, the 

 shell resembles T. excavata, Sowerby, and still more T. hyalina, 

 Sower by, both from Port Jackson. Of these two species the shell 

 only is known. The shell and animal seem to me to be distinct from 

 T. norfolkensis, Sowerby. 



2. Tethys Tryoni, Meinertzhagen, 1880. Plate 23, fig. 12 ; Plate 36, 



fig. 6. 



Aplysia Tryoni, Mein., T.N.Z.I., xii, 1879 (1880), 270. Tethys Tryoni, 

 Mein., Man. Conch. (1), xvi, 98 ; Index, 69. 



Shell horny, flexible, convex, elongated. There is no other sculp- 

 ture except fine concentric growth-lines. The whole shell consisting 



18-Moll. N.Z. 



