96 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



a sub-p;enus under the name of Sinodia. His isocardia group is quite 

 too restricted, including only that species, D. liipinus, and D. modeata, 

 the last being probably only a variety of lupitius. None of his other 

 groups are satisfactory, and it is often difficult to understand his 

 reasons for associating or separating certain species. Thus he puts 

 linda in the exoJeta section and Africana in another one (No. 6), 

 whereas, in reality, lincta and Africana are so closely allied that some 

 consider the latter to be only a variety of the former. < 



I cannot find that anyone else dealt systematically with the genus I 

 between the years 1862 and 1902, but in the latter year Dr. W. H. ' 

 Dall published a " Synopsis of the Veneridfe 'V and under the head 

 of Losinia he definitely proposed six sections, each with a special 

 name, in addition to the group represented by the type species, 

 1). Africana. As most of these are additions to conchological 

 nomenclature, they must be critically examined in order to ascertain 

 what other species besides the one selected as a type should be referred 

 to each section ; further, whether all the known species of Dosinia can 

 be distributed among these sections. Their names and types are as 

 follows : — 



Dosinia, sensu stricto. Type, B. Africana (Gray). 

 Orbiculus, Megerle. ,, B. exoleta (Lin.). 



Ausfrodosinia, Dall. ,, D. anus (Phil.). 



Dosinisca, Dall. ,, D. alata (Keeve). 



Dosi)iorbis, Dall. ,, D. hilumdata (Gray). 



Dosi)iidia, Dall. ,, D. concenirica (Born). 



Dosinella, Dall. ,, D. angulosa (Phil.). 



The principal characters of the type section {Dosinia, s.s.) as 

 defined by Dr. Dall are — " Lunule impressed small, escutcheon narrow, 

 elongate, bordered on each side by a ridge or keel ; middle cardinals 

 often grooved . . . ; pallial sinus angular, ascending, usually narrow 

 and extended forward at least halfway from the posterior to the 

 anterior adductor." He further remarks that " the form of the 

 escutcheon differs in this group from an obscure flattening, often 

 unequal in the two valves, to a distinctly keeled area with sculpture 

 differing from that outside the boundary, but in the series of species 

 almost every gradation between these forms may be observed". 

 No mention, however, is made of any of the species he would refer to 

 the group ; but under Orbiculus he remarks that D. prostrata (Linn.) 

 is a typical Dosinia, a view with which I cannot agree unless he 

 intended also to include D. Japonica, D. scabriuscula, and other species 

 hereafter noted. 



It is conceivable that he meant to accept Homer's " Section of 

 D. Africana ", but if so lie shouhl have said so, for that section 

 exhibits some obvious inconsistencies, including as it does D. fibula, 

 but not D. cretacea, and excluding D. lincta, which is so closely allied to 

 D. Africana. All these species certainly belong to this section as well 

 as D. Adansoni, D. Orbignyi, and D. alta. Probably also D. lupinus 



^ Proc. U.S. National Museum, vol. xxvi, p. 335, 1902. 



