Bd VI: 4) THE ECHINOIDEA. 1 1 1 



Fig. 17. Valve of small globiferous pedicellaria of Aastrocidaris caualiculata, from the 

 inside. 7 %- 



» 18. Abactinal radiole of Austrocidaris canaliculata. 6 ' s /x. 



Plate XV. 



Fig. 1. Part of ambulacrum of Arbacia crassispina. 8 /i. 



» 2. Valve of triphyllous pedicellaria of Arbacia Dufresnii. I75 /i. 



» 3. Part of ambulacrum of Arbacia Dufresnii. s/i. 



» 4. The point of an actinal spine of Arbacia crassispina. IS /i. 



» 5. Valve of ophicephalous pedicellaria of Arbacia crassispina. 7 % 



» 6. » > » » » » Dufresnii. 70 1 1. 



» 7. » » s> » » crassispina. 7 % 



» 8. The point of an actinal spine of Arbacia Dufresnii. IS /i. 



» 9. Ocular plate of Arbacia Dufresnii. 



» 10. Stalk of ophicephalous pedicellaria of Arbacia Dufresnii. I2 5/ t . 



» 11. Ocular plate of Arbacia crassispina. r «/x. 



» 12. Ambulacral plates of Tetrapygus niger. IO /i. 



» 13. Valve of tridentate pedicellaria of Arbacia Dufresnii. 5 %. 



» 14. » » » » » » crassispina. 7 °/i. 



» 15. Ambulacral plates of Tetrapygus niger. IO /i. 



Plate XVI. 



. r. Tridentate pedicellaria of Sterechinus Agassi zii. 5 %- 



2. Valve of tridentate pedicellaria of Loxcchinus a/bus. 65 /i. 



3. Globiferous pedicellaria, small form, of Notecliinus magellanicus (comp. Fig. 19). 5 %- 



4. Sphaeridia of Loxcchinus a/bus. I7 %- 



5. Tridentate pedicellaria of Loxechinus a/bus. 5 °/ t . 



6. The point of a secondary spine of Notecliinus magellanicus. 5 %. 



7. » » » » » » » Sterechinus Agassizii. 5 °/i. 



8. Group of spicules from tubefoot » » » 225 /i. 



9. Spicules from tubefoot of Notecliinus magellanicus ; a. fully developed, b. develop- 



mental stage. 225 /i. 



10. Abnormal, two-headed triphyllous pedicellaria of Notecliinus magellanicus ; the left 



head slightly restored. 7 %- 



11. Secondary spine of young Notecliinus magellanicus. 5 %. 



12. Primary » » » » » s %. 



13. Outer part of secondary spine, with the point regenerated, of Sterechinus Agassi- 



zii. 5°/,. 



14. Valve of ophicephalous pedicellaria of Loxechinus albus. 6s /i. 



15. Globiferous pedicellaria of Sterechinus Agassizii. + s /i. 



16. Valve of triphyllous pedicellaria of Loxechinus albus. I7 °/i. 



