Dosinia.] PELECYPODA. 977 



Colour brownish or yellowish-white. Interior white, polished outside 

 the pallial line. Margins smooth, sharp. Hinge-plate moderately 

 broad, arcuate ; right valve with 4 cardinals, the two anterior teeth 

 subparallel, oblique, directed forwards : the third long and oblique, 

 directed backwards, longitudinally grooved above ; the fourth parallel 

 to the latter, a fine, low, sharp lamella ; 2 low divergent lateral teeth 

 in front ; left valve with 3 strong cardinals, the front tooth oblique, 

 high, directed forwards, the other two cardinals oblique and directed 

 backwards; the median cardinal strongest, with a tubercle and a 

 short low arm in front ; 1 short low tubercular anterior lateral tooth. 

 Ligament external, extending behind from the umbones to the end 

 of the hinge-plate. Adductor-scars unequal, the anterior high and 

 narrow, the posterior suboval. Pallial line distinct, at some distance 

 from the margin ; pallial sinus diagonal, pointing toward the upper 

 end of the anterior scar, acutangular, extending to the centre of the 

 disc. 



Length, 25 mm. ; height, 24 mm. ; diameter, 13-5 mm. 



Type in the U.S. National Museum, Washington. 



Hob. Bay of Islands, type (Archer) ; near Channel Island, 

 Hauraki Gulf, in 25 fathoms ; Auckland Harbour ; Queen Charlotte 

 Sound, in 10 fathoms (" Challenger " Exp.) ; Kermadec Islands 

 (Captain Bollons). 



Fossil in the Miocene and Pliocene. 



Sect. 2. ORBICULUS, Megerle, 1811. 

 Type : Venus exoleta, L. 



In this section there is no escutcheon, the pallial sinus is very 

 long, and the anterior lateral is smooth and strong, otherwise it agn-.-s 

 with Dosinia, s. str. (Dall.) 



2. Dosinia cserulea, Reeve, 1850. Plate 60, fig. 8. 



Artemis ccerulea, Reeve, Conch. Icon., vi, 1850, f. 25 ; Thes. Conch., ii, 1852, 

 664, pi. 142, f. 43, 44. Dosinia ccerulea, Reeve, Nov. Conch., Dosinia, 

 1862, 71, pi. 13, f. 4; Suter, T.N.Z.I., xxxviii, 318. 



Shell fairly large, thick and heavy, moderately convex, sub- 

 quadrangularly ovate, somewhat inequilateral, with close, sharp, and 

 strong concentric riblets, greyish- white. Beaks not much raised, con- 

 vex, acute, approximate, directed forwards. Anterior end regularly 

 convex, the dorsal margin shortly excavated in front of the umboues ; 

 posterior end slightly longer, narrowly rounded at the middle, the 

 dorsal margin long, convex, descending ; basal margin semicircular. 

 Lunule short, cordate, striated, well impressed. Escutcheon indi- 

 cated only by a shallow depression on each side. Sculpture 

 consisting of regular, sharp, and dense concentric riblets, the 

 sharp edges directed upwards, the interstices of the same width 

 as the riblets. Colour greyish- white, the umbones light orange, 



