— 8 — 



All available common names have been carefully considered and a 

 single name selected with regard to (1) actual use (no "manufactured" 

 names have been introduced), (2) appropriateness and (3) distinc- 

 tiveness so that confusingly similar names may be avoided. If the 

 connnon names are to be of any use there must be uniformity and it 

 is earnestly requested that the names here proposed be used, for even 

 though they seem strange to some, all have been carefully considered 

 and represent, as far as possible, names in actual use. 



KEY TO THE EDIBLE BIVALVES OF CALIFORNA 



The figures are partially diagrammatic and all. except as noted, are placed 

 in the same position, that is, with the dorsal or back side up, the ventral or lower 

 side down, the anterior or head end to the reader's left and the posterior or hinder 

 end to the right. As most represent the interior of the shell this must then be the 

 right valve. The following reference letters are used for all : 



aa — anterior adductor muscle scar, 

 bs — byssal scar, 

 bn — byssal notch. 



c — cartilage, 

 cp — cartilage pit. 



e — escutcheon. 

 1 — ligament. 



m — membrane (covering hinge region.) 

 pa — posterior adductor muscle scar, 

 pi — pallia! line. 

 ps — pallial sinus. 



r — rib. 



u — umbo. 



Fio. 2. Pecten cir- 

 cularis. One-half nat- 

 ural size. 



Fig. .1. Saxidoinus nutt(tUi. One - luilf 

 natural size. 



a. Only one adductor muscle (the posterior) present: mantle edges not fused, hence 

 no siphon or pallial sinus ; adults either rigidly attached, usually by shell, or 

 entirely free and capable of swimming actively, always lying on one side, 

 never I)urrowing. (See Fig. 2; compare with aa and Fig. 3). 



b. Valves unlike, the right with a deep notch, apparently a hole, for the passage 

 of a byssus by which it is attached. 



Rock oysters 



c. Left valve with two muscle scais (adductor and byssal muscle) ; shell light 

 but not delicate, surface of shell roughened, not translucent. 



Monia macroschisma 



p. 26 ; pi 3 , tigs. 1, 2 



