PLATE 31. 
1-17. Micropetalon purpureum A. AGassiz and H. L. Cuarx. 
1.— Interior view of the actinal side. 
2.— Anal system, seen from the outside. 
3.— Stalk and head of an ophicephalous pedicellaria, measuring 1.13 mm. long, from the abactinal 
side, at the ambitus, from the right posterior interambulacrum. 
4.— Ophicephalous pedicellariae, 0.27 mm., valve B in centre, from right anterior interambulacrum 
from the abactinal side. 
5.— Valve A, 0.28 mm. exterior view. 
6.— Valve B, 0.26 mm. exterior view. | Of a single ophicephalous pedicellaria, from the abactinal side 
7.— Valve C, 0.25 mm. interior view. / at the ambitus, from right anterior interambulacrum. 
8.— Valve C, 0.25 mm. exterior view, from the right anterior interambulacrum, from the abactinal side. 
9.— Spine, 1.92 mm. long, from right anterior interambulacrum, near the edge of the actinostome. 
10.— Spine, 1.44 mm. long, from right anterior interambulacrum towards the summit. 
11.— Spine, 0.95 mm. long, from odd anterior ambulacrum, at the edge of actinostome. 
12.— Spine, 0.65 mm. long, from right posterior interambulacrum, near the summit. 
13.— Spine, 0.81 mm. long, detail of an end, from right anterior interambulacrum, from the abactinal 
side. 
14.— Disk plate, 0.21 mm. in diameter, seen from above, from odd anterior ambulacrum, from the 
actinal side. : 
15.— Actinal tube-foot, 0.50 mm. long, seen in profile, from the edge of actinostome, in odd anterior 
ambulacrum. 
16.— Abactinal tube-foot, diameter of the disk 0.11 mm. from the apex. — 
17.— Spicules from the tube. 
The magnification is identical in figures of the same order. 
