660 EXPLANATION OF THE TLATES. 



Fig. B. Pectiniira infemalis, showing the disk and the variations of 

 the " naked plates," x 3. 

 C. Ophropinax stellatus, showing the arrangement of the radial 

 and interradial plates on the disk, x 2. 



Plate IX. 



Fig. A. Cucumaria semperi. 



B. Coloclrirus tuberculosus. Spicules seen from the side and 



from below. 



C. Actinocucumis difficilis. 



D. Tliyone okeni. Calcareous ring and oesophagus. 



E. a and b, spicules of Stereoderma validum ; c, c7, the same, 



Been a little out of focus; e, a smaller spicule ; /, a spicule 

 seen in side view. 



F. Phyllopliorus proteus. F'. Parts of calcareous ring. 



G. Holotliuria macleari. 



All but figs. D and F' are magnified 220 times, and are figures of 

 spicules; D is magnified f, F' twice. 



Plate X. 



Fig. A. Antedon carpenteri, nat. size. A a, A 5, A c. First, second, 

 and typical pinnules, x 3. 



B. pumila, x 3. B «, B b. First and fourth pinnules, 



x3. 



C. loveni, nat. size. C a, C b, C c. First, third, and typical 



pinnules, x 3. C d, C e. Dorsal surface of arms in regions 

 marked x and y in C, x 3. 



Plate XI. 



Fig. A. Antedon bidens, X 2. A a. A cirrus, x 4. A 6, A c. First 

 and third pinnules, x 4. 



B. decipiens, x f . B a. Arm-joints from above, x 4. 





