966 PELECYPODA. [Eulamellibranchia. 



the anterior cardinal, appressed to the ventral lamina ; 2 anterior 

 and 2 posterior lateral lamella?, the upper ones thin, straight, sharp, 

 the lower ones thicker and higher, distally raised ; left valve with 

 2 cardinals, the anterior bifid, strong, the upper and slightly posterior 

 tooth small, extending over the resilifer, a rather distant somewhat 

 oblique accessory lamella in front, which is high and triangular, and 

 almost continuous with the anterior lateral tooth, which is slightly 

 raised in front ; the posterior lamella is strong, convex ; resilifer 

 large, oblique, broadly triangular, apically roofed. Ligament small, 

 narrow, and external in front of the umbones, but triangularly sunk 

 behind and coming into contact with the resihum. Adductor-scars 

 unequal, the anterior smaller, pyriform, rather deep, the posterior 

 larger, roundish, and shallow. Pallial sinus large, reaching to very 

 near the middle of the disc, angularly rounded in front. 



Length, 92 mm. ; height, 63 mm. ; diameter, 34 mm. (type). 



Type in the Mus. Hist. Nat., Paris. The type of M. notata, Hutton, 

 is in the Dominion Museum, Wellington. 



Hob. North and South Islands, but nowhere common ; occa- 

 sionally washed up after gales. The type specimen of M. notata was 

 dredged in 25 fathoms near Stewart Island. 



Fossil. Miocene and Pliocene. 



4. Mactra ovata, Gray, 1843. Plate 60, fig. 3. 



Spisula ovata. Gray, Dieff. N.Z., 251. Mactra omta, (I ray. Conch. Icon., 

 viii, 1854, f. 30; Crit. List, 43. Hemimactra ovata, Gray, C.M.M., 63; 

 Hutton, P.L.S. N.S.W., ix, 518. Mactra (Stand,lla) oratti. Gray, Ereb. & 

 Ter., 5, pi. 2, f. 2. Standetta urata. Gray : Hutton, J. de Conch., xxvi, 

 45 ; M.N.Z.M., 139 ; Index, 90. Mactra delute, Gould, P. Bost. S.N.H., 

 iii, 1850, 215 ; U.S. Expl. Exp., xii, 391, f. 503. M. inflate, Hutton, 

 C. Tert. M., 1873, 18 ; J. de Conch., xxvi, 4(i. M. lamta, Hutton, T.N.Z.I., 

 xvii, 1884 (1885), 331 ; Plioc. M., 70, pi. 8, f. 81 ; Index. 90 ; Suter, 

 T. N.Z.I., xxxviii, 319. Standetta cequalis, Webster, T. X.Z.I., xxxvii, 

 1904 (1905), 280, pi. 10, f. 13. 



Shell rather large, thin, inequilateral, rounded ovate, yellowish- 

 brown, smooth, the valves ventricose, posteriorly gaping. Beaks 

 tumid, acute, incurved, contiguous. Anterior end shortest, sloping 

 rapidly, obtusely rounded, the dorsal margin straight ; posterior end 

 narrowly rounded, the dorsal margin straight, descending ; basal 

 margin convex, straightened and ascending anteriorly. Anterior area 

 excavated near the beaks, without a distinctly marked areola, broad, 

 striate ; posterior area broad, rounded, excavated near the beaks. 

 Sculpture consisting of irregular and delicately undulating concentric 

 lines, crossed by fine irregular wrinkles at the posterior end. Epi- 

 dermis thin, silky, yellowish-brown. Colour yellowish-brown, the dorsal 

 areas and beaks usually blackish. Interior yellowish on the upper 

 parts, bluish-white towards the base, lightly shining. Margins smooth, 

 sharp, rather thin. Hinge : Right valve with 2 cardinals, the posterior 

 almost vertical, directed over the resilifer, the. anterior cardinal thin, 



