GO LAMELLIBRANCHIATA. 



forated disc with a minute central fissure ; siphonal eud plain or 

 ornamented with from one to eight ruffles. 

 Red Sea. Java. Australia. 



* 4. A. novse zealandiae, Lamark, i.e., vi., p. 21. Shell 



with the valves ovate, posteriorly angularly expanded ; sheath rude, 

 irregular, somewhat cylindrical ; frill indistinct, with two to three 

 rows of tubes, which are short, large, free ; disc convex, with the per- 

 forations very few. (Reeve) 



FAMILY GTLYCIHEIIID^. 



Equivalve, thick, gaping at both ends ; hinge with a rudimentary 

 cardinal tooth ; ligament external, solid and prominent, placed upon a 

 more or less strong callosity ; pallial impression irregular, sinuated 

 behind. 



SAXICAVA. 



Oblong, irregular, generally equivalve, inequilateral, slightly gaping 

 at both ends ; hinge linear, without teeth or with a rudimentary one 

 on each valve ; ligament external ; pallial line siuuated, not con- 

 tinuous. 



World-wide. 



5. S. arctica, Linnaeus ; 8. australis, Lamark, Anitn. sans vert., 

 vi., p. 153 ; Hiatella minuta, Gray, Dieff. N.Z., ii., p. 252. Shell more 

 or less swollen, longitudinally striated. White. Height, '35 ; length, 

 '65. Very variable in shape. 



Cosmopolitan. 



PANOPJEA. 



Equivalve, inequilateral, gaping at each end, thick ; ligament ex- 

 ternal on prominent ridges, one prominent tooth in each valve ; pallial 

 impression strong, with a more or less deep sinus. 



Europe. Cape of Good Hope. Australia. Patagonia. 



6. P. zealandica, Quoy, I.e., iii., p. 547. Oval, inequilateral, 

 sub-compressed, widely gaping, longitudinally plicated, urnbones obtuse, 

 recurved. White. Height, 3'3 ; length, 4'9 ; breadth, 2'15. 



Common. Chatham Islands. 



* 7. P. SOlandri, Gray, Dieff. N.Z., ii., p. 255. Oblong, ventri- 

 cose, rounded in front, rather narrower and truncated behind, smooth. 

 White. Much more ventricose than the last. (Gray.) 



FAMILY CORBULLDJG. 



Inequivalve, thick, closed ; hinge composed of a single conical re- 

 curved tooth in the right valve, received into an indentation in the left 

 valve. 



CORBULA. 



Inequilateral, gibbous, rounded in front and produced posteriorly ; 

 ligament internal ; pallial sinus slight ; pedal scars distinct from the 

 adductors. 



Widely spread. 



