986 PELECYPODA. [Eulamellibmnchia. 



umbones at about the anterior third of length. Beaks tumid, raised, 

 incurved and directed forwards, sharply pointed. Anterior end shorter, 

 regularly convex, the dorsal margin lightly concave, descending ; 

 posterior end convex, dorsal margin very little curved, oblique ; 

 ventral margin convex. Lunule oblong-cordate. Escutcheon obsolete. 

 Sculpture consisting of coarse, flattish, and depressed concentric ribs, 

 crossed by very distinct radiate striae. Colour yellowish - white. 

 Interior white, porcellanous. Margins finely crenulate. Hinge-plate 

 solid, broad and rather short, concave posteriorly ; right and left 

 valve with 3 cardinals, the anterior teeth oblique, short, and thin ; the 

 median teeth subvertical, strong, grooved ; the posterior teeth unequal 

 in the two valves ; in the right the tooth is oblique, long, and rather 

 stout, grooved, in the left valve it forms an elongate long and narrow 

 lamella ; the anterior lateral tubercle obsolete. Ligament strong, 

 inset, but visible on the outside, extending from the beaks to the 

 posterior end of the hinge-plate. Adductor-scars subequal, oval, not 

 deep. Pallial sinus short, triangular, ascending, and free. 



Length, 41 mm. ; height, 35 mm. (type). Length, 47 mm. ; height, 

 41mm.; diameter, 28mm. Length, 39 mm. ; height, 36 mm. ; dia- 

 meter, 26 mm. 



Type, from the Pliocene, in the Canterbury Museum, Christchurch. 



Hab. Stewart Island (C. Traill) : near the Snares, in 50 fathoms ; 

 Auckland Islands (Captain Bollons). 



Fossil in the Pliocene. 



Subfam. VENERIN.E. 



Animal with comparatively short siphons, which are more or less 

 separate from each other. The foot is hatchet-shaped and, in the 

 adult, not byssiferous except among the nestlers. The young undergo 

 their development outside of the parent shell. 



This subfamily is characterized by the total absence of lateral 

 teeth. 



SYNOPSIS OF GENERA. 



A. Margins of valves crenulated ; 3 cardinals in each valve ; pallial 



sinus small, triangular ; lunule well circumscribed ; es- 

 cutcheon not distinctly defined . . . . . . CHIONE. 



B. Margins of valves smooth ; 3 widely divergent cardinals in each 



valve ; pallial sinus small, rounded ; lunule long, narrow, 



feebly circumscribed ; escutcheon not denned . . . . GOMPHINA. 



C. Margins generally smooth ; 3 cardinals in each valve, anterior 



right and posterior left entire ; pallial sinus free, rather 

 large ; lunule not constant, lanceolate ; escutcheon ill de- 

 fined . . . . . . . . . . . . PAIMIIA. 



D. Margins smooth or crenulate ; 3 cardinals in each valve, the 



anterior right and posterior left entire ; pallial sinus rather 

 large, free, blunt in front ; escutcheon, if present, distinct 

 only on the left valve . . . . . . VENERTJPIS. 



