100 PROCEEDINGS OF THE 5JALAC0L0GICAL SOCIETY. 



group. Some of these species I separated in 1908 under the name of 

 Sinodia with D. trigona as type; others remain which must now he 

 considered, and chief of these is the group which includes D.Japonica, 

 Desh., and D. scabriuscula (Pliil.). 



For tliis group I propose the name Phacoxoma, from cjjuko^ and aUmi 

 = lentil-body. This section I define as follows. 



Phacosoma (sectio nova). 



Type, Dosinia Japonica, Reeve. 



Shell orbicular, convex; lunule deeply impressed; escutcheon rather 

 wide and pouting raesially on each side of the ligament, defined by 

 raised lamellose ridges. In the left valve a strong anterior lateral, 

 generally rugose ; a narrow tall anterior cardinal, an oblique median 

 wliich is not bifid, but rugosely striated, and runs back so tliat its 

 outer edge is nearly parallel to the posterior tooth. Pallial sinus fairly 

 deep, angular, and generally horizontal. Margin of right valve grooved 

 posteriorly. 



To this section the following other species belong : scabriusculd 

 (Phil.), biscocta (Reeve), ccerulea (lUeeYe), pfosfrata (Linn.), exasperata 

 (Phil.), contusa (Reeve), ptibescens (Phil.), labiosa (Romer), lameUata 

 (Reeve), Roemeri (Dunker), and suhrosea (Gray). In this group 

 I should id so place JD. bilunulata (Gray), which Dr. Dall separates 

 as a section by itself. 



AYith respect to the Sinodia group it differs so much from all the 

 sections above mentioned that I regard it as a sub-genus, and now 

 give a condensed description of it. 



Sinodia, Jukes-Browne. 



Type, Bosinia trigona, Reeve. 



Shell trigonal, oval, or orbicular. Lunule non-existent, but part 

 of the anterior side is circumscribed by a faintly impressed line. 

 Escutcheon area not defined, but sometimes depressed. In the left 

 valve the anterior lateral is strong and distant from the anterior 

 cardinal ; the middle cardinal is entire, solid, and equidistant from 

 the other two, but united at the top to the anterior tooth. Both 

 valves are grooved on the posterior margins, the right having a long 

 deep groove, the left a shorter and shallower one. The pallial sinus 

 is variable, but generally rather short and rounded. 



Most of the species are trigonal, and all have an expanded anterior 

 side; but D. excisa (Cheni.) is sub-orbicular and B. glob a (Melvill) 

 is more completely orbicular, still in its hinge and other internal 

 characters it resembles trigona and splimricnla. 



CoEDiopsis, Cossmann. 



Lastly, there are some fossil species which I regard as belonging to 

 the genus Bodnia, but which have been separated by M. Cossmann 

 as a sub-genus of Meretrix under the name of Cordiopsis. The type 

 of this group is a well-known Oligocene fossil, the Cytherea incrasmta 

 of Sowerby, which I referred to Sinodia in 1908, remarking that it 

 agreed with Sinodia in all the points which I then mentioned, and 



