68 LAMELLIBEAKCHIATA. 



in a deep central pit ; a minute anterior hinge tooth and 1 lateral teeth 

 in each valve ; muscular scars deep, pallial sinus small. 

 West Indies. India. Chili. Australia. 



47. M. chemnitzii, Desliayes, Anim. sans vert., vi., p. 134. 

 Ovato-oblong, sub-equilateral, thick, white, smooth, covered with a 

 thin pale brown epidermis ; ligament plate deep, nearly vertical ; . a 

 strong anterior hinge tooth in the left valve ; lateral teeth sub-equal ; 

 pallial sinus small. Height, 1'5 ; length, 2 25. 



Abundant. The Natives call this shell " kokota," or " pipi." 



48. M. CUnGata, Lanark, vi., p. 112 ; M. sul-triangulata, Gray, 

 Dieff. N.Z., ii., p. 252. Trigonal, solid, smooth, posterior end very 

 short, sub-truncated ; white, covered with a thin light brown epidermis ; 

 ligament plate rather deep, slightly inclined to the front ; the posterior 

 lateral tooth of the left valve higher than the anterior ; pallial sinus 

 moderate. Height, 2 25 ; length, 3 25. 



Abundant. Chatham Islands. 



The Natives call this shell " tuatua." 



* 49. M. ventricosa, Gray, Die/. N.Z., ii., p. 252. Ovate, 

 wedge-shaped, truncated behind, thin, ventricose, opaque white, smooth, 

 slightly concentrically striated ; covered with a thin nearly transparent 

 horn-coloured epidermis ; edge thin ; lateral teeth short, smooth, com- 

 pressed, close to the cartilage pit, the front one of the left valve the 

 largest ; pallial sinus not quite reaching to the centre of the disc. 

 (Gray.) 



50. M. elongata, Quoy, I.e., iii., p. 518. Ovato-trigonal, thick, 

 rather flattened, posterior end shorter, attenuated, sub-angular, plicated ; 

 anterior end rounded ; slightly gaping at both ends, smooth, concen- 

 trically striated ; cartilage plate produced, inclining backwards ; "hinge 

 teeth obsolete ; anterior laterals notched ; pallial sinus deep, reaching 

 nearly to the centre of the shell. White or yellowish, with a thin pale 

 brown epidermis. Height; 2'75 ; length, 4'5. 



* 51. M. lata, Reeve. Shell triangularly ovate, broad, compressed, 

 concentrically densely irregularly striated, stria? more grooved at the 

 sides ; posterior side rounded, anterior much shorter, angularly trun- 

 cated ; umbones rather flattened. Whitish, covered with a pale yellow 

 horny epidermis. (Reeve) 



* 52. M. OValiS, Reeve. Shell oblong oval, rather thin, com- 

 pressed towards the margin, nearly equilateral, posterior side a little 

 the narrower ; shining white ; rather obscurely striated ; partially 

 covered with a blackish epidermis. (Reeve.) 



* 53. M. Spissa, Reeve. Shell triangularly oblong, thick ; an- 

 teriorly rather sharply angled and truncated ; posteriorly rounded ; 

 compressed at the umbones ; posterior area rather broad, sub-concave ; 

 light fuscous white, irregularly striated. (Reeve) 



* 54. M. nOVSD zealandise, Reeve. Shell oblong ovate, trans- 

 verse, rather solid, nearly equilateral, sides rounded, anterior rather 

 the shorter ; whitish, irregularly striated, covered with a thin fulvous 

 white shining horny epidermis. (Reeve.) 



