JUKES-BROWNE : SYNOPSIS OF THE VENERID^. 63 



trimaculata is finely striated or grooved, and more oblique in form, 

 the posterior end being somewhat produced ; the latter group includes 

 L. sulcatina, Lam., and Dmie philippiana, Hanley. 



(jenus Saxidomds, Conrad, 1857. 



Tlie true position of tliis genus as a member of the Meretriciuae 

 was established by Dr. Dall in 1902.^ The anterior laterals are placed 

 so near tbe anterior cardinals that tbey have been mistaken for 

 supernumerary cardinals, and the shell has consequently been located 

 near Tapes and Venerupis. It is, however, more nearly related to 

 Callista than to any other genus, and is to some extent linked with 

 Callista by the Japanese species C. chishumana, which has a corrugated 

 shell and oblique anterior lateral teeth. The dentition of Saxidomm 

 differs from that of Callista much in the same way as the hinge of 

 Dosinia differs from that of Pitaria. The animal is said to have long 

 and closely united siphons. 



Only three living species of Saxidotnus are known, namely, 

 S. nuUalli, Conrad {=aratus, Gould, and maximus, Anton), S. gigantens, 

 Desh., and S. purpuratus. Sow. They all come from the North 

 Pacific, ranging from California northwards to Alaska and Japan. 

 In time they go back to the Eocene of California. 



Type, S. mdtalU, Conrad. 



Shell oval, concentrically corrugated ; without defined lunule or 

 escutcheon; slightly gaping posteriorly. Ligament large and con- 

 spicuous. Hiuge-plate curved and narrow, with irregular teeth; 

 left valve with an oblique anterior lateral and three cardinals, which 

 are narrow and near together, the posterior being separate from the 

 nymph ; right valve with two small anterior laterals and three 

 cardinals, of which only the posterior is grooved. Valve-margins 

 smooth and without any groove in either valve. Pallial sinus deep 

 and horizontal. Muscular impressions large ; pedal scar opening 

 irregularly into that of the adductor. 



Genus Dosinia, Scopoli, 1777. 



This genus and its subdivisions have also been fully discussed in 

 a previous paper, to which the reader is referred.^ Here, therefore, 

 I need only give a generic definition and an abbreviated synopsis of 

 the sections and sub-genera which I think worth recognition. The 

 Dosinorbis of Dall was based on D. hilumdata, which has a defined 

 area outside the true lunule ; similar areas exist in Chione rohorata 

 and Ch. calophijlla, and are only of specific importance. The sub- 

 genera Sinodia and Cordiupsis may be regarded as links between the 

 genera Dosinia and Pitaria. 



Synonyms : Orbiculus, Megerle (1811) ; Artemis, Poll in Oken 

 (1815); Asa, Leach in Basterot (1825); Arctoe, Risso (1826); 

 Exoleta, Brown, 1827. Not Dosina, Gray (1838). 



Shell sub-orbicular, more or less compressed, concentrically striated 



^ Proc. U.S. Nat. Museum, vol. xxvi, p. 356. 

 2 Proc. Malac. Soc, vol. x, p. 95, 1912. 



