1032 PELEC'YPODA. [EulameUibraiirkia. 



common in the North ; in muddy sand from low-water mark to about 

 5 fathoms. Kermadec Islands (Captain Bollons). 



Maori. Pakira (teste Hutton). 



Fossil in the Pliocene. 



9. Myodora subrostrata, E. A. Smith, 1880. Plate 55, figs. 16, n. 



Myodora subrostrata, E. A. Smith, P.Z.S., 1880, 584, pi. 53, f. 6 ; Hutton. 

 P.L.S. N.S.W., ix, 516 ; Index, 88. M. ovata, Reeve : Hutton, C.M.M., 

 62 ; J. de Conch., xxvi, 45 ; M.N.Z.M., 137. not of Reeve. 



Shell subtrigonally ovate, posteriorly subtruncated, subequilateral, 

 fairly solid, the right valve moderately convex, the left valve flat, 

 rather coarsely concentrically ribbed. Anterior end sharply curved, 

 slightly longer, the dorsal margin faintly convex, slowly descend- 

 ing ; posterior end narrowly subtruncated, rather acuminated, the 

 dorsal margin faintly convex, oblique : ventral margin curved and 

 feebly sinuated posteriorly, giving the shell a somewhat rostrated 

 appearance. Sculpture : Right valve with a trace of a shallow de- 

 pression down the posterior side, with somewhat distant, coarse, 

 rounded, concentric ribs ; left valve with similar but somewhat 

 closer and sharper concentric ribs ; both valves with microscopic 

 dense concentric lines, interrupted by more distant radial lines. 

 Epidermis thin, light brown, persistent at the ventral margins. 

 Colour dirty-white. Interior white, pearly, with a single impressed 

 ray, curving from the umboiies to the anterior part of the pallia! sinus 

 in the left valve, and a, little farther within the valve in the right 

 one. Margins smooth, sharp. Hinge with a small triangular resilium, 

 and a small pellucid clavicle. Adductor-scars unequal, rather high 

 up, the anterior elongate, the posterior round. Pallial sinus small, 

 convex. 



Diameter Ant. -post., 18mm.; dorso-ventral, 14-5: thickness, 



5 mm. 



Type in the British Museum. 



Hob. New Zealand (Colonel Bolton and Mus. Cuming) ; Stewart 

 Island (C. Traill) ; Foveaux Strait, in 15 fathoms ; Plimmerton 

 (A. Hamilton) ; Channel Island, Hauraki Gulf, in 25 fathoms ; near 

 Cuvier Island, in 38 fathoms (Captain Bollons). 



Fossil in the Miocene and Pliocene. 



Fam. CHAMOSTREIDJE, Fischer. 



Animal having the mantle largely closed ; a fourth pallial orifice 

 present ; pedal orifice small. Siphons very short and separate. 

 Foot small, compressed. Labial palps rather long, obtuse. Gill large, 

 oval, deeply plicated, extending to between the palpi, united behind 

 with the opposite gill, but divided into two parts by a deep oblique 

 groove, the superior part being free and composed of a single gill. 



