PLATE IX. 



Fig. 1. — A dorsal veiw of the pericardial cavity, mantle not removed, 

 p. a. Posterior adductor. au. Auricle. 



r. Posterior retractor. v. Ventricle, 



p. m. Mantle. p. Pericardium, 



o. b. Organ of Bojanus. 



Fig. 2. — A dorsal view of the pericardial cavity, mantle removed, 

 p. a. Posterior adductor. v. Ventricle, 



p. r. Posterior retractor. au. Auricle. 



r. Rectum. o. b. Organ of Bojanus. 



p. Pericardial cavity. 

 Fig. 3. — The valve leading from the auricle to the ventricle, 

 val. Valve. au. Auricle, 



v. Ventricle. 



Fig. 4. — Organ of Bojanus or renal organ. 



p. a. Posterior adductor, 

 r. Rectum, 

 a. Anus, 

 p. r. Posterior retractor, 

 p. Pericardial cavity, 

 v. Ventricle. 

 p. g. Opening leading from the 

 floor of the pericardium to 

 glandular sac. 



o. b. c. Opening leading from the 

 non -glandular sac to the 

 branchial chamber. 



Non-glandular sac. 



Glandular sac. 



Opening leading from the 

 glandular 

 dular sac. 



Auricle. 



i. g. s. 



g. s. 



o. e. s. 



Fig. 5.— Floor of the pericardium, showing the r two openings (o. p. g.) into 



the renal organ. 

 Fig. 6. — Floor of non-glandular sac, showing openings into the glandular 

 sac and branchial chamber, and the openings from the glandular 

 sac as shown in Fig. 5. 

 Fig. 7. — Diagram showing more plainly than fig. 4 the passage leading from 

 the floor of the pericardium to the branchial chamber. 

 Fig. 8. — Showing nerves in place. 



c. g. 

 c. c. 



ps. g. 

 ps. c. 



Cerebral ganglion. 



The commissural cord con- 

 necting the cerebral gang- 

 lia. 



Posterior ganglia. 



Commissural cord ' connect- 

 ing the cerebral and pos- 

 terior ganglia. 



P-g- 

 pe. c. 



Pedal ganglion. 



Commissural cord connect- 

 ing the pedal and cerebral 

 ganglia. 



Anterior mantle nerve. 



The nerve whose branches 

 are the nerves of the gills. 



Posterior mantle nerve. 



