Dosinia.] PELECYPODA. 981 



very slowly descending ; basal margin semicircular. Lunule vertically 

 raised, cordiform, short, bounded by a narrow groove, finely lamellate. 

 Escutcheon not defined. Colour light yellowish-brown. Interior white, 

 dull, the scars polished. Margins smooth, sharp. Hinge-plate well 

 developed, slightly arcuate ; right valve with 4 cardinals, the anterior 

 short and thin, almost horizontal ; the second vertical, a little larger, 

 triangular, and bifid ; the third long and stout, very oblique, directed 

 backwards, deeply grooved ; and the last cardinal forming a long, 

 slender, and low lamella close to the third tooth ; 2 anterior short 

 lateral teeth, the upper one larger and continuous with the first cardinal ; 

 left valve with 3 cardinals, the anterior forming an oblique narrow 

 lamella ; the second is stout, triangular, deeply bifid, and slightly 

 oblique ; the third is long, a sharply raised thin and very oblique 

 lamella ; the anterior lateral tooth is well developed, of the same 

 length as the anterior cardinal, somewhat corrugated. Ligament strong 

 and rather long. Adductor-scars unequal, the anterior smaller, pyri- 

 form, the posterior larger, roundly ovate. Pallial sinus long, narrowly 

 triangular, ascending, its angle pointing above the anterior scar. 



Diameter Ant.-post., 36 mm. ; dorso-ventral, 36 mm. : thickness, 

 23 mm. (type). Diameter Ant.-post., 31 mm. ; dorso-ventral, 29 mm. : 

 thickness, 18mm. (Recent specimen from Evans Bay.) 



Type in the K.K. Hofmuseum, Vienna. 



Hob. Auckland Harbour ; Evans Bay. Wellington Harbour (Cap- 

 tain Bollons) ; Banks Peninsula (Iredale) ; Stewart Island (A. Hamil- 

 ton) ; Chatham Islands. 



Fossil in the Miocene and Pliocene. 



The late Professor Tate recorded the species found fossil in yellow 

 limestone of the sea-cliffs at Edithburgh, on west side of St. Vincent 

 Gulf. 



Subfam. MERETRICIN.E. 



Shells with smooth or concentrically sculptured surface ; generally 

 smooth inner margins ; a single anterior lamella in the left valve, 

 received in a pit on the opposite valve ; 3 cardinal teeth in each valve : 

 lunule defined by an incised line ; the escutcheon not or ill defined ; 

 pallial sinus varying from obsolete to deep and angular. 



SYNOPSIS OF GENERA. 



A. Shell smooth, polished . . . . . . MACROCALLISTA. 



B. Shell with elevated concentric lamellae . . . . . . CYTHEREA. 



Genus 1. MACROCALLISTA, Meek, 1876. 



MacroccMista, Meek, Pal. Upper Missouri, 1876, 179. Type : Venus nimbosu, 

 Solander'= gigantea, Gmelin. Chione, Gray, 1838; not of Megerle, 1811, 

 or Gray, 1851. Dione, Gray, 1851 ; not of Hiibner, 181(5. Cullista, 

 Morch, 1853 ; not of Leach, 1852. Chionella, Cossmann, 1880. Macro- 

 callista, Meek : Dall, Proc. U.S. Nat. Mus., xxvi, 1902. 351 ; Trans. 

 Wagn. Free Inst., iii, pt. 6, 1251. 



Animal with the siphons of moderate length with papillose orifices, 

 the tubes united for a great part of their length ; the margin of the 



