Corbula.] PELECYPODA. 101 1 



4. Corbula Haastiana, Button, 1878. Plate 55, fig. 5. 



Corbula Haastiana, Button, J. de Conch., xxvi, 44 ; M.N.Z.M., 135 ; P.L.S. 

 N.S.W., ix, 514 ; Index, 88. 



Of the unique type specimen the left valve is lost, and in his 

 diagnosis the late Captain Hutton undoubtedly took the right valve 

 for the left. 



Shell subtrigonal, very inequivalve, covered with a brown epi- 

 dermis : rounded anteriorly, absolutely keeled posteriorly ; left valve 

 very finely striated, the right deeply grooved ; ventral margin sinu- 

 ated posteriorly ; yellowish-white. (Hutton, emended.) 



Right valve concentrically closely ribbed, the interstices linear. 

 Hinge with a very deep pit below the beak, with a short lamellar 

 elevation anteriorly, and 2 lamellae close together at the hind end, 

 followed by a blunt, tooth-like projection on the hinge-plate. 



Length, 10 mm. ; height, 10 mm. ; diameter of right valve, 6 mm. 



Hob. Lyttelton (Dr. von Haast). 



Remark. The right valve seems to agree with the characters 

 mentioned for the section. 



Fam. SAXICAVID^l, C4ray. 

 Olycymeridce, Fischer. 



Animal with the mantle extensively closed, with a small pedal 

 orifice ; siphons elongate, covered by a chitinous sheath, and wholly 

 or largely united ; gills prolonged into the branchial siphon ; foot 

 small. 



Shell - substance cellulo - crystalline, earthy, with a conspicuous 

 epidermis ; valves equal, free, rude, and often irregular, more or less 

 gaping and elongated, not fully covering the animal ; adductor-scars 

 often irregular, the pallial line discontinuous or irregular, the sinus 

 distinct ; shell - margins smooth ; area obsolete ; ligament and re- 

 silium external, parivincular, seated on strong nymphs, sometimes 

 widely extended ; hinge without laterals, with few feeble or obsolete 

 subumbonal cardinals. 



Cretaceous to Recent. 



KEY TO GENERA. 



A. Shell small, irregular in form, not very widely gaping ; pallial 



sinus shallow . . . . . . . . . SAXICAVA. 



B. Shell large, elongately oblong, very widely gaping behind ; pallial 



sinus large, broadly triangular .. .. .. .. PANOPEA. 



Genus 1. SAXICAVA, F. de Bellevue, 1802. 



Saxicava, F. de Bellevue, Bull. Soc. Philom., No. 62, 1802, 5, 10. Type : 

 Mya arctica, L. Hiatella, Daudin, 1802, &c. 



Animal perforating or free, attached by its byssus ; mantle-lobes 

 united and thickened in front ; palpi small, free ; siphons large, united 

 nearly to their ends, orifices fringed. 



