1905.] NATURAL SCIENCES OF PHILADELPHIA. 569 



Explanation of Plate XXXYII. 

 (All figures are magnified 250 diameters.) 



Pseudopotamilla hrevibranchiata, figs. 1 to 7. 



Fig. 1. — Dorsal thoracic capillary seta from somite "^'I. 



Fig. 2. — Long abdominal capillary seta from somite XX. 



Fig. 3. — Spatiilatc thoracic seta from somite VI. 



Fig. 4. — Thoracic avicular uncinus from somite VI. 



Fig. 5. — Abdominal avicular uncinus from somite XX. 



Fig. 6. — Pick-shaped seta from somite VI. 



Fig. 7. — Another view of the end of the same. 

 Pseudopotamilla occelata, figs. S to 14. 



Fig. 8. — Dorsal thoracic capillary seta from VI. 



Fig. 9. — Long abdominal capillary seta from XX. 



Fig. 10. — Spatulate thoracic seta from VI. 



Fig. 11. — Thoracic avicular uncinus from VI. 



Fig. 12. — Thoracic avicular uncinus from IX. 



Fig. 13. — Abdominal avicular uncinus from XX. 



Fig. 14. — Pick-shaped uncinus from VI. 

 Pseudopotamilla intermedia, figs. 15 to 22. 



Fig. 15. — Dorsal thoracic capillary seta from YI. 



Fig. 16. — Short abdominal capillary seta from XX. 



Fig. 17. — Spatulate thoracic seta from VI. 



Fig. 18. — Thoracic avicular uncinus from VI. 



Fig. 19. — A typical avicular uncinus from the last thoracic somite (X). 



Fig. 20. — Portion of another from the same torus showing a larger crest. 



Fig. 21. — Abdominal avicular uncinus from XII. 



Fig. 22. — Pick-shaped seta from somite VII. 

 Pseudopotamilla splendida, figs. 23 to 27. 



Fig. 23. — Long abdominal capillary seta from XXI. 



Fig. 24. — Spatulate thoracic seta from VI. 



Fig. 25. — Thoracic avicular uncinus from VI. 



Fig. 26. — Abdominal avicular uncinus from XX. 



Fig. 27. — Pick-shaped seta from VI. 

 Pseudopotamilla anoculata, figs. 28 to 33. 



Fig. 28. — A sliorter abdominal capillary seta from XXVI. 



Fig. 29. — Face view of the bladed portion of the same. 



Fig. 30. — Spatulate thoracic seta from VI. 



Fig. 31. — Thoracic avicular uncinus from A^I. 



Fig. 32.— Abdominal avicular uncinus from XXA'I. 



Fig. 33. — Pick-shaped seta from VI. 



