142 Scientific Proceedings, Royal Dublin Society. 



EXPLANATION OF PLATES. 



Plate I. 



Fig. 1. — Diagram of a transverse section through the upper portion of 

 the oesophageal region of S. venusta. Specimen y. 



Fig. 2. — Diagram of a transverse section through the lower portion of 

 the oesophageal region of 8. venusta. Specimen a. 



Fig. 3. — Transverse section through the middle of the oesophageal 

 region of 8. venusta. Specimen a. 



Fig. 4. — Diagram of a transverse section through the lower portion of 

 the oesophageal region of S. venusta. Specimen {3. 



Fig. 5. — Transverse section through the upper portion of the oesopha- 

 geal region of a specimen of S. nivea. 



Plate II. 



Fig. 1. — Transverse section through the oesophageal region, near the 

 oral disk of S. venusta. Specimen /?. 



Fig. 2. — Transverse section through the lower portion of the oesopha- 

 geal region of 8. venusta. Specimen y. 



Fig. 3. — Transverse section through the middle of the oesophageal 

 region of 8. miniata. Specimen y. 



Fig. 4. — Diagram of the arrangement of the mesenteries in S. miniata. 

 Specimen a. 



Fig. 5. — Diagram of the arrangement of the mesenteries in S. miniata. 

 Specimen (3. 



Fig. 6. — Transverse section through a small specimen of S. troglodytes, 

 taken near the oral disk. 



