Rochefortia.] PELECYPODA. 931 



1. Rochefortia donaciformis, Angas, 1878. Plate 54, tigs. 5, a, b. 



Mysdla donaciformis, Angas, P.Z.S., 1878, 863, pi. 54, f. 13, Tate, T.R.S. 

 S.Aust., ix, 99. Rochefortia donaciformis, Angas : Tate and May, P.L.S. 

 N.S.W., xxvi, 433 ; Medley, op. cit., xxvii, 7, pi. 1, f. 10-14 ; Suter, 

 T.N.Z.I., xxxix, 270. 



Shell small, quadrately cuneate, moderately solid, equivalve, 

 very inequilateral, subventricose, compressed towards the base, white, 

 shining, finely concentrically ridged. Beaks inconspicuous, approxi- 

 mate, with a minute round prodissoconch. Anterior end much longer, 

 produced, the dorsal margin slightly arcuate, descending, acutely 

 convex towards the broadly rounded basal margin ; posterior end 

 short and abruptly descending, narrowly rounded below. Sculpture 

 consisting of somewhat unequal sharp concentric lines. Colour white. 

 Interior pure-white with a few greyish concentric bands. Margins 

 sharp, smooth. Hinge : Right valve with an elevated strong oblique 

 cardinal in front of the resilifer and a second slender one in front of 

 the former ; a faint cardinal bordering the resilifer posteriorly ; on 

 each side an elongated fine lateral, leaving a groove between them and 

 the border of the valve ; left valve with an anterior and posterior 

 simple lamella. Resilium central, triangular. Adductor-scars distinct, 

 the anterior larger. Paliial line simple. 



Diameter Ant.-post., 4'8 mm. ; dorso-ventral, 3'3 mm. : thickness, 

 2 mm. 



Type in the British Museum. 



Hab. Port Pegasus, Stewart Island, in 18 fathoms ; Snares and 

 Bounty Islands, in 50 fathoms (Captain Bollons) ; Campbell Island 

 (Professor Chilton). Australia and Tasmania. The type is from Al- 

 dinga Bay, South Australia. 



2. Rochefortia reniformis, Suter, 1908. Plate 54, figs. 4, . 



Rochefortia reniformis, Suter, T.N.Z.I., xl, 1907 (1908), 357, pi. 27, f. 12. 



Shell small, elongately oval, fairly solid, equivalve, inequilateral, 

 compressed, minutely reticulated. Beaks small, sharply pointed, ad- 

 jacent, directed backwards ; prodissoconch minute, oval, smooth and 

 shining. Anterior end longer, its dorsal margin slowly descending and 

 faintly convex, anterior margin regularly rounded ; posterior end 

 convex, the dorsal margin straight, sloping ; basal margin straight, or 

 more often with a slight sinus in the middle Sculpture consisting of 

 subequal and inequidistant strong concentric riblets, sharply rounded, 

 with the interstices of about the same width ; as they are receding 

 from the beak they are getting much stronger and more distant ; 

 some well-marked periods of rest are usually visible at regular in- 

 tervals ; radial fine threads are reticulating the concentric sculpture. 

 Epidermis thin, light brown. Colour light brown, whitish when the 

 epidermis is lost. Interior white, porcellanous, the growth-periods 



30* 



