REPORT ON THE ECHINOIDEA. 285 



Fig. 2. Abactinal system of same, somewhat enlarged. 



,, 3. Actinal system of same, somewhat enlarged. 



,, 4 a. Tip of spine from the actinal side to show the shape of shoe, enlarged. 4 h. The 

 same seen from the side of the shoe. 4 c. Another spine, with differently- 

 shaped shoe, seen from the side. 



PLATE X'\ 



Plexirechinus hothryoides, Ag. (figs. 1, 2), p. 108. 

 Fig. 1 . Abactinal system of specimen measuring 1 8 mm. in diameter. 

 ,, 2. Enlarged view of part of sides of the test of same specimen. 



Phormosoma luculentum, A. Ag. (figs. 3-7), p. 97. 



,, 3. Denuded segment of test from the abactinal side. 



,, 4. View of actinal segment of same specimen. 



,, 5, 6. Sheathed spines, similar to those of A. grubii, from the abactinal part of the 



test close to the apical system. 

 ,, 7. One of the large peclicellarise of the actinal surface of the test. 



Astropyga radiata, Gray (figs. 8, 9). 



„ 8. Interior view of interambulacral plates of the actinal side, showing the deep pits 

 of the base of the primary tubercles. 



,, 9. Interior view of interambulacral plates of the actinal plates, showing the lapping 

 of the edges and the two plates which make up each half of the inter- 

 ambulacral zone at that point. 



PLATE X\ 



Phormosoma hursarium, A. Ag. (figs. 1-9), p. 99. 



Fig. 1. Seen from the abactinal side ; natural size. 

 ,, 2. Same, seen from the actinal side. 



,, 3. Denuded portion of actinal surface of the test and actinostome of same. 

 ,, 4. Abactinal system and denuded portion of the abactinal surface of same. 

 „ 5. Ambulacral and interambulacral plates of abactinal surface of same about one- 

 third from the edge of the test (-f ). 

 ,, 6. Plates of actinal surface of test about one-third from the edge of the test (f ). 

 ,, 7. Plates from the very edge of the test, showing the accumulation of miliaries 



forming a rudimentary fasciole (f ). 

 ,, 8. Enlarged view of the abactinal system (f ). 



