Chione.] PELECYPODA. 989 



by the valve-margins ; the edges of the right nymph and of the left 

 posterior cardinal with interlocking rugosities. (Ball.) 



KEY TO SPECIES. 



A. Shell transversely oval ; concentric lamellae high, striate, with 



tubular processes, about 6 on an adult valve ; margins smooth 



inside . . . . . . . . disjecta. 



B. Shell ovate, subquadrate ; concentric lamellae not so high, laciniate, 



12 to 16 on an adult valve ; margins finely crenate inside . . Yatei. 



2. Chione disjecta, Perry, 1811. Plate 61, fig. 5. 



Venus disjecta, Perrv, " Coiichology," 1811, pi. 58, f. 3. Chione disjecta, 

 Perry: Pritchard and Gatliff, P.Pv.S. Vic., xvi (ii.s.), 122. Anaitis 

 disjecta, Perry, Index, 89. Venus lamellata, Lamarck, A.s.V., v, 1818, 

 592 ; Thes. Conch., ii, 725, pi. 160, f. 175 ; Conch. Icon., xiv, pi. 18, f. 78. 

 Chione lamellata, Lamarck, C.M.M., 69 ; Hut-ton, J. de Conch., xxvi, 4!i ; 

 M.N.Z.M., 147. 



Shell transversely oval, thin, but little inflated, with high, distant 

 concentric lamellae and 2 posterior ridges descending from the umbones 

 to the lower posterior angle and to the posterior part of the ventral 

 margin. Beaks not much raised, somewhat inflated, biangulate 

 behind, incurved and directed forwards, situate at about the anterior 

 fourth of length. Anterior end short, narrowly rounded, the dorsal 

 margin a little concave ; posterior end truncated, sub vertical, angled 

 above towards the long, slightly convex, and very slowly descending 

 dorsal margin ; ventral margin broadly rounded, angled on meeting 

 the posterior margin. Lunule distinct, raised, radially lamellate, 

 lanceolate. Escutcheon distinctly limited by a keel on each side, long 

 and narrow. Sculpture consisting of distant concentric lamellse, 

 which are recurved, striated on the outside, and produced into semi- 

 tubular processes on the 3 posterior ridges ; the interstices with 

 fine growth-lines. Colour white, the lamellae light-pinkish. Interior 

 yellowish-white, smooth, dull. Margins smooth, but the upturned 

 outer lamella very strongly crenulated. Hinge rather slender ; right 

 valve with 3 cardinals, the anterior small, subvertical ; the second 

 close and parallel to it, somewhat stouter, grooved ; the posterior 

 cardinal horizontal, long, not very strong, grooved ; left valve with 

 the anterior cardinal subvertical, thin, and short ; the second oblique, 

 triangular, deeply grooved ; the third very oblique, thin, and long. 

 Ligament strong, deep-set, extending from the beaks to the posterior 

 end of the hinge-plate. Adductor-scars very superficial, unequal, the 

 anterior oval, the posterior roundish. Pallial sinus free, moderately 

 large, triangular, pointed in front. 



Length, 58 mm. ; height, 35 mm. ; diameter, 25 mm. 



Type of Lamarck in the Mus. Hist. Nat., Geneva. 



Hob. Two valves (one broken) from Cook Strait are in the Do- 

 minion Museum, Wellington. Australia and Tasmania. Found in 

 deep water on oyster-banks (Angas). 



