Zenatia.] PELECYPODA. 971 



adjacent, very anterior ; lunular area encroaching on the inner 

 dorsal margin, hardly visible externally ; pallial sinus very deep, 

 gapes conspicuous, the valves hardly touching except at the hinge 

 and ventral margin ; ligamenu lanceolate, short, somewhat sunken, 

 not set off by any shelly barrier from the pit ; chondrophore oblique, 

 large, posteriorly depressed below the hinge-plate, resilium homo- 

 geneous and continuous between the valves ; dental armature con- 

 centrated ; left cardinal large, with an obscure accessory lamella 

 between it and the ligament ; a short high anterior lateral parallel 

 with the anterior arm of the cardinal, above which descends the 

 lunular area ; behind the ligament a very small narrow posterior 

 lateral (often lost) lies adjacent to the dorsal margin ; valves 

 below the cardinals reinforced by an obscure thickened ray of shell- 

 substance, but which does not support the chondrophore ; upon this 

 ray, behind the adductors and below the ventral sinus of the car- 

 dinal, are the scars of the pedal retractors ; right valve with the 

 cardinal wide, hardly coalescent above, with 2 very small posterior 

 but no anterior laminae ; both the cardinals are wholly exterior to the 

 pit, (Ball.) 



Distribution. New Zealand and Australia. 



Fossil in the Miocene and Pliocene of New Zealand. An 

 allied genus, Zenatiopsis, Tate, is recorded from the Miocene of 

 Victoria. 



I. Zenatia acinaces, Quoy and Gaimard, 1835. Plate 60, figs. 6, a. 



Lutraria acinaces, Q. & G., Voy. Astrol., iii, 1835, 545, pi. 83, f. 5, 6 ; Dieff. 

 N.Z., 251 ; Conch. Icon., viii, 1854, f. 14. Zenatia acinaces, Q. & G., 

 Ad. G.R.M., pi. 102, f. 1 ; C.M.M., 64 ; Crit. List, 43 ; M.N.Z.M., 140 ; 

 Button, J. de Conch., xxvi, 46 ; P.L.S. N.S.W., ix, 518. Z. zelandica, 

 Gray, A.M.N.H. (2), x, 143. Lutraria Deshayesi, Reeve, Conch. Icon., 

 viii, 1854, f. 1 ; Crit. List, 43. Zenatia Deshayesi, Reeve, M.N.Z.M., 140. 

 Z. solenoides, Deshayes, P.Z.S., 1854 (1855), 72. Z. Cumingiana, Desh., 

 op. cit., 72. 



Shell moderately large, oval, elongated, compressed, rounded and 

 gaping on both ends, equivalve but very inequilateral, concentrically 

 striated, yellowish to* brown. Beaks small, very little raised, approxi- 

 mate, incurved. Anterior end very short, occupying about one-fifth 

 of the length of the shell, convex ; posterior end rounded or sub- 

 truncated, the dorsal margin long, slightly concave or straight, 

 horizontal ; basal margin straight, curved towards both ends. 

 Lunule, encroaching on the inner dorsal margin. Sculpture consisting 

 of fine close concentric stria; with oblique fine folds of the epidermis 

 .at both ends. Epidermis thin, light brown, shining, extending a little 

 beyond the margins of the valves. Colour yellowish-white in young 

 specimens, brown in adult shells. Interior bluish-white, shining, 

 slightly iridescent, with a prominent callosity behind the anterior 

 scar, and 2 fine ridges descending from the beaks, one to the anterior 



