PLATE 18. 



Mastigethus errans Chamberlin. 



Figures 1-6. 



1. — Parapodium of middle region, caudal view. X 45. 



2. — Distal end and socket of compound seta, side view. X 1110. 



3. — The same, frontal view. X 1110. 



4. — Simple ventral seta, distal end, from middle region of body. X 281. 



5. — Distal end of compound seta. X 281. 



6. — Aciculum, distal and proximal ends. X 281. 



Nans simplex Chamberlin. 



Figures 7, 8. 



7. — Distal portion of ventral seta, larger form, from middle region of body. X 1075. 

 8. — The same, smaller form of same parapodium. X 1075. 



