APPENDIX 



57 1 



Mussels may easily be found by searching the shallow part of ponds 

 and streams, usually partly buried in the mud. 

 The Freshwater I. Note protrusion of foot, and current through 

 Mussel, siphons (Fig. 220 A). 



2<z. Note in side view umbo, lines of growth, position 

 of hinge, ends of shell (Fig. 220 A) ; in dorsal view, umbo, 

 lines of growth, ligament (Fig. 221). 



rp.b.._;^ 



Fig. 408.- 



-Part of the dorsal side of a swan mussel in which the 

 pericardium has been opened. 



an., Auricle ; d.s., margin of dorsal siphon ; g. t hinder tips of gills, fused to form 

 floor of cloacal chamber ; p.ad., posterior adductor muscle ; pr., posterior re- 

 tractor muscle; nn., rectum; rp.o., renopericardial opening; v., ventricle; 

 v.s., margin of ventral siphon (opened out by spreading the mantle). 



Note between the posterior adductor muscles the fusion of the mantle edges for a 

 short distance, roofing in the cloacal chamber just above the dorsal siphon. 



b. Remove left valve of shell by separating it from edge of mantle 

 and cutting through attachment of adductor muscles (keep 

 edge of scalpel close to shell). Note : mantle lobes, their 

 thick edges, siphons, two adductor, two retractor, and 

 protractor muscles (Fig. 222, left mantle lobe cut away). 



t. On inside of shell, note: marks of attachment of muscles; 

 pallial line (Fig. 220 B). 



