— 13 — 



ff. Shell oval or round in outline, conspicuously lliin. srowtli lines usually 

 faint, always more or less irregular. 

 S. Shells without conspicuovis periostracimi, whitish. 



h. Ligament depressed so as not to be visible from the side; siplionate 

 end of shell not produced, valves deeply arched. 

 iVIetis Metis alta 



p. 42 ; pi. 11 , fig. 2 



lih. Ligament not depressed, hence A'isible from tlie side; siphonate end 



of shell more or les.s produced, valves not deeply arched. 



Macoma 



i. Si|ili<inatc (Mid of shell pioiluced and bent to right; valves about 

 tMiuall.\- arelu'd, [lallial sinus in left reaching anterior muscle 

 scar; I'cuiiid in |)r(iti',ted nuid or muddy sand. 



Bent- nosed clam M. luisntd 



]>. a:'.: pi. II. fig. :!: pi. ij, fi.o.s. i. 2 



Fig. 12. Macoma nasuta. Natural 

 size. (A) Interior right valve. (B) 

 Interior left valve. 



ii. Siphonate end of shell not produced; left valve much flatter than 

 right, pallial sinus not reaching anterior muscle scar in 

 either valve ; found deep in loose exposed sand. 



White sand clam M. srcta 



p. 44 ; pi. 12 , figs. .T, 4 , pi. 13 ; fi.g. 1 



gg. Shell with distinct blue or purplish color and conspicuous glossy 

 reddish brown periostracum ; right valve much flatter than left ; 

 found in coarse sand or gravel. 



Purple clam i^duguinolaria nuttalli 



p. 46 ; pi. 14 , fig.s. 2, 3 



ee. Li.gament in part external liut with a larger internal part (cartilage) ; 

 pallial sinus not united witli pallial line ; shell round in outline, fairly 

 heavy, tinged with pink at margins. 



Flat clam Semele clecisa 



p. 45 ; pi. 13 , fig. 2 



