408 MARINE INVERTEBRATES 
Anatomy of a pelecypod, Anodonta cygnea. The animal with most of the left mantle lobe removed, 
a, excretory opening; @.ad., anterior adductor muscle; a.7., anterior retractor muscle; au., left 
auricle; d.p.a., dorsal pallial aperture; ex. sph., exhalant siphon; /t., foot; in. sph., inhalant 
siphon; kd., kidney; 1. ext. gl., left external gill; J. ext. plp., left external labial palp ; 1. int. gl., left 
internal gill; 1. int. plp., left internal labial palp; 1. m., cut edge of left mantle lobe; mth., mouth; 
p.ad., posterior adductor musele; pe., pericardium; p.7., posterior retractor muscle; pre., pro- 
tractor muscle; ret., rectum; r.m., right mantle lobe; v, ventricle; v. m., visceral mass. 
gor Te 
Anatomy of a pelecypod, Anodonta cygnea. Dissection from the left side. a, excretory opening; 
a.ad., anterior adductor muscle; a. ao., anterior aorta; a. v.ap., auriculo-ventricular aperture; bl., 
urinary bladder; c¢. pl. gn., cerebropleural ganglion; d.d., duct of digestive gland; d. gl., digestive 
gland; d.p.a., dorsal pallial aperture; ex. sph., exhalant siphon; /t., foot; g. ap., genital aperture. 
gon., gonad; gul., gullet; él. j., interlamellar junction ; in. sph., inhalant siphon ; int., intestine ; kd. 
kidney; m, mantle; mth., mouth; p.ao., posterior aorta: p.ad., posterior adductor muscle; pe., 
pericardium ; pd. gn., pedal ganglion; r.ap., renalaperture; 7. au., right auricle; ret., rectum; 
Tr. p. a., reno-pericardial aperture ; st., stomach; ty., typhlosole; v., ventricle; v. gn., visceral ganglion ; 
w.t., water-tubes. 
