394 MR PATRICK GEDDES AND. MR FRANK E. BEDDARD 
DESCRIPTION OF PLATES. 
PLATE XIX, 
View of a portion of surface of test of Hchinus sphera, showing spine and various kinds of 
pedicellarize grouped round it, x 60. 
a. Ophiocephalous. 
b, Tridactyle. 
c. Gemmiform. 
d, Trifoliate. 
Pirate XX. 
Ophiocephalous pedicellarve (figs. 1-14. 
Fig. 1. Calcareous valve viewed from inner surface, x 120. 
Fig. 2. Epithelium of stalk treated with silver nitrate, x 120. 
Fig. 3. Same more highly magnified, x 540. 
Fig. 4. Base of valves showing how the fibres of stalk are wrapped round the semicircular 
arches, x 120. 
Fig. 5. Looped terminations of stalk fibres freed from their attachment to semicircular arches, 
and spread out x 200. 
Fig. 6, Epithelial cells continuous with long processes, x 540. 
Figs. 7 and 8 are views of the triangle of approximator muscles, in a peculiar state of contrac- 
tion, in which both extremities of each muscle mass is swollen, x 30, 
Fig. 9, Central granular core of soft part of stalk, showing nuclei and a few ensheathing 
fibres, x 540, 
Figs. 10, 11. Coiled elastic plates, x 540. 
Fig. 12. Fibres from approximator muscles of head ; (a) fibre treated with osmic acid, showing 
striation ; (b) fibre broken across, showing sarcolemma; (c) plain fibre prepared with 
alcohol; (d) fibres with spindled-shaped swelling, showing nuclei, x 540. 
Fig. 13. Cross section of head which has been prepared with gold chloride, so that calcareous 
parts are dissolved away and not shown. In the centre of muscular triangle is seen the 
looped extremity of stalk fibres, and outside the three coiled plates of elastic tissue, x 120. 
Fig. 14. Section showing base of calcareous valves, x 120. 
Tridactyle pedicellarie (figs. 15-17). 
Fig. 15, Calcareous valve viewed from inside, x 120. 
Fig. 16. Section through head just above base of calcareous valves, x 120, 
Fig. 17. Section showing base of calcareous valves, x 120. 
