PLATE LXII. 
Explanation of the Letters. 
A. Axial cord of the ray. Z. Basiradial ligament. 
a’. Its branches in the dorsal skeleton. id. Dorsal ligament between the ray-joints. 
ad. Its upward extensions into the plated perisome of “i. Interarticular ligament. 
the ventral side. lp. Labial plexus. 
ae. Ambulacral epithelium. M. Mouth. 
ai. Primary interradial cords. m. Muscle. 
. Anambulacral plate. 
Basal. 
. Radial blood-vessel. 
c. The bands of more or less calcified connective tissue in | 
the body-cavity. 
. Fibrillar sheath round the vascular axis of the stem. 
. Interradial portion of the circular commissure. 
. Ambulacral nerve. 
. Its oral ring. 
. Oral blood-vascular ring. 
. First and third radials. 
. Rectum. 
. Plug of calcareous tissue within the radial funnel. 
. Spinelets on the anambulacral plates. 
ch. Cavities of the chambered organ. ste. Subtentacular canal. 
ch’. Their downward prolongations into the stem. sub, Subambulacral plate. 
chn. The nodal enlargements of these peripheral vessels. sy. Syzygy. 
ev. Cirrus-vessel. V. Central vascular axis of stem. 
D,, Ds. Second and fifth distichals. W. Radial water-vessel. 
Sg. Fore-gut. wp. Water-pore. 
G, Gut. wr. Water-vascular ring. 
g. Its epithelial lining. wt. Water-tube. 
gv. Genital vessel. a. Plexiform gland. 
Intervisceral blood-vessel. 
Its ventral end which joins the labial plexus 
Explanation of the Colours. 
Black—The nervous system, both ambulacral and antambulacral. 
Green—The water-vascular system. 
Red-—The blood-vascular system and the plexiform gland. 
Diagrammatic longitudinal section of a Pentacrinus decorus. On the right side of the 
figure the section cuts the anal tube, and on the left side it passes along a ray 
and the base of an arm. 
