NOTES ON AGELACRINIDAE AND LEPADOCYSTI- 
NAE, WITH DESCRIPTIONS OF THRESHERO- 
DISCUS AND BROCKOCYSTIS 
Aug. F. Foerste 
CONTENTS 
1. Introduction 
2. Character of surface used for support by Ordovician Agelacrinidae 
3. Orientation of Agelacrinus pileus on sloping supports 
4. Curvature of ambulacral rays , 
5. Cause of reversal of curvature of right jiosterior ray of Agelacrinus 
6. Reversal of curvature in Streptaster 
7. Supporting surface of Agelacrinus cincinnatiensis probably more horizontal 
than in Agelacrinus pileus 
8. Solar curvature in the Devonian Agelacrinites and Lepidodiscus 
9. Aboral surface of Lepidodiscus 
10. Mobile marginal part of peripheral ring 
11. Rigid inner band of peripheral ring 
12. Vertical ridges on plates of inner band of peripheral ring 
13. Central part of aboral surface 
14. Interambulacral plates 
15. Trimerous origin of ambulacral system 
16. Cover plates of ambulacral rays 
17. Peristomial plates 
18. Floor plates of Devonian and Carboniferous Agelacrinidae 
19. Floor plates of Ordovician species referred to Agelacrinus 
20. Floor plates of Streptaster 
21 Floor plates of Thresherodiscus 
22. Basal extensions of lateral covering plates of the ambulacral rays' 
23. Anal pyramid 
24 Location of the anus in the Agelacrinidae 
25. Origin of ambulacra’ system of Agelacrinidae 
26. The ornamentation of the surface of the thecal plates 
27. The central or substomial cavity of Agelacrinus pileus 
28. The central or substomial cavity of Streptaster septembrachiatus 
Description of several Ordovician Agelacrinidae 
29. The use of the generic terms Agelacrinites and Lepidodiscus 
30'.' Thresherodiscus ramosa, gen. et sp. nov. 
31. Agelacrinus vetustus, sp. nov. 
32. Agelacrinus faberi, Mdler 
33. Agelacrinus austini, sp. nov. 
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