Diplodon.] PELECYPODA. 943 



with strongly pronounced rest-marks, and between them a few lines 

 of growth, all close together and foliated at the anterior end ; in 

 adult specimens the middle part has distinct radiate nodulous 

 sculpture, partly A -shaped. Epidermis olive-green, waxy, but nearly 

 the. whole surface is covered with a thin ferruginous coating. Interior 

 bluish-white, pearly, a little blotched with olive in the umbonal cavity, 

 where there are rather large and deep dorsal scars. Hinge : Eight 

 valve with 2 compressed small pseudo-cardinals, the upper anterior 

 tooth is a small smooth lamella, the lower tooth is more elevated, 

 conoidal, and strongly crenate ; the lateral tooth is almost straight, 

 thin and rugose at its posterior portion. In the left valve there is 

 a rather long compressed lower anterior rugose pseudo-cardinal, the 

 upper tooth is quite rudimentary ; the upper lateral tooth is a little 

 higher and more rugose behind than the other. Ligament small, 

 not much raised. Adductor-scars not deep. 



Length, 45 mm. ; height, 24 mm. ; diameter, 8 mm. 



Type in my collection. 



Hob. Lake Manapouri, in 60 ft., type (Lucas and Hodgkin). 



Subsp. rugatus, Hutton, 1883. Plate 59, fig. 8. 



Unio rugatus, Hutton, N.Z.J.S., i, 1883, 478 ; T.N.Z.I., xvi, 216 ; Hedley 

 and Suter, P.L.S. N.S.W. (2), vii, 603. U. Mcnziesi rugafa, Hutt, : 

 Suter, J. de Conch., xli, 291. Diplodon Menziesi rugatus, Hntt. : Simp- 

 son, Proc. U.S. Nat. Mus., xxii, 1900, 889 ; Suter, T.N.Z.I., xxxvii, 238. 



Shell oval, rather thin, anterior end compressed, rounded, finely 

 striated ; posterior subventricose, very rudely concentrically corru- 

 gated ; dorsal margin ascending, straight ; ventral margin flatly 

 rounded ; cardinal teeth rugose, not striated. (Hutton.) 



Right valve with the anterior pseudo-cardinal oblique, very small, 

 the posterior tooth strong, compressed, pectinated, the lateral tooth 

 corrugated at its posterior end ; left valve with 2 stout compressed 

 pseudo-cardinals, which are subequal and also pectinated, the 2 laterals 

 distally corrugated. Anterior adductor-scar much impressed. Mar- 

 gins much thickened posteriorly outside the simple pallial line. 



Length, 52 mm. ; height, 34 mm. ; diameter, 17 mm. (type). 



Type in the Canterbury Museum, Christchurch. 



Hob. South Island : Lake Pearson (type) ; Upper Waimakariri 

 River ; Lake Letitia, Mount White ; Cheviot ; Lake Kanieri ; Wairau 

 River; Owaka Stream, Clutha. North Island: LakeWaikare; Kopua- 

 ranga River. 



Subsp. Websteri, Simpson, 1902. Plate 59, fig. 9. 



Diplodon Websteri, Simpson, "The Nautilus," xvi, July, 1902, 30: Suter, 

 T.N.Z.I., xxxvii, 23(5. Unio (Diplodon) Websteri, Simps. : Webster, 

 T.N.Z.L, xxxviii, 311, pi. 39, f. 5. D. Websteri, Simps. : Suter, T.N.Z.I., 

 xxxix, 270 ; Dall, Proe. U.S. Nat. Mus., xxxv, 1908, 181, pi. 30, f. 1, 2. 



Not Unio Websteri, Wright, 1888. 



Shell long, rhomboid, compressed or subcompressed, inequilateral. 

 Beaks subcompressed, pointed, their sculpture apparently a few 



