Protocnrdia.] PELECYPODA. 1 001 



valves. Colour pale fulvous or pinkish-white, with radial bands of 

 pink, which become obsolete by age. Interior yellow at the upper 

 central part, pink on the anterior and posterior upper ends and also 

 on the hinge-plate, white and shining at the ventral part of the valves. 

 Margins finely denticulated by the radial sculpture. Hinge-plate 

 very narrow, arcuate ; right valve with 1 conical cardinal and a 

 second minute cardinal in front of it, 1 anterior and 2 posterior lateral 

 teeth, the former arising from the umbonal cavity, and having some- 

 times a second obsolete lamella above ; left valve with 2 cardinals, 

 the anterior tooth larger, erect, the posterior at some distance and 

 small ; 1 anterior and 1 posterior lateral. Ligament short, external. 

 Adductor-scars subequal, ovate. Pallial line indistinct, entire. 



Length, 27 mm. ; height, 22 mm. ; diameter, 17 mm. 



Type in the British Museum. 



Hob. North and South Islands and Stewart Island, in depths 

 varying from a few to 100 fathoms. Off Great Barrier Island, in 

 110 fathoms ; near Cuvier Island, in 38 fathoms ; Hauraki Gulf, in 

 25 fathoms ; off Wanganui, in 20 fathoms ; Queen Charlotte Sound, 

 in 16 fathoms ; off Oamaru, in 40 fathoms ; Molyneux Bay, in 20-46 

 fathoms ; north-east of Wreck Reef, in 50 fathoms ; Wet Jacket 

 Arm, in 12 fathoms ; Preservation Inlet ; Stewart Island, in 15-20 

 fathoms ; Milford Sound, in 100-120 fathoms (Professor Chilton). 

 Australia and Tasmania. 



Fossil. Miocene and Pliocene. 



SUBORDER 6. MYACEA. 



Eulamellibranchia in which the mantle is closed to a considerable 

 extent ; the siphons are well developed, the gills much folded and 

 frequently prolonged into the branchial siphon. The foot is com- 

 pressed, and generally byssiferous. The shell gaping, with a pallia! 

 sinus. 



Fam. PSAMMOBIID^E, Gray. 



Animal with the siphons very long and quite separate ; foot large, 

 flattened from side to side ; and pointed. 



Shell as in the Tettinidce, but usually more equivalve and less 

 twisted, with more conspicuous epidermis and nymphs, broader 

 hinge-plate, and a wider posterior gape ; lateral laminae on the hinge 

 wanting, and the cardinals sometimes 3 in the valve ; ligament ex- 

 ternal and conspicuous ; no defined area. 



Tertiary to Recent. 



SYNOPSIS OF GENEKA. 



A. Right valve with 2, left valve mostly with 1, strong grooved or 



bifid cardinals ; pallial sinus deep, but not extending far 



beyond the vertical of the beak . . . . . . PSAMMOBIA. 



B. Two cardinals in each valve, erect, small, not grooved ; pallial 



sinus extending much beyond the vertical of the beak . . SOLETELLINA. 



