Cd. 
chn. . 
EXPLANATION OF THE PLATES. 
The following letters are employed throughout all the Plates :— 
Axial cord of the ray or arm. 
Axial cord of a pinnule. 
Branches of the axial cord in the skeleton. 
Connective-tissue fibres between the 
anambulacral plates. 
The parambulacral extensions of the axial 
cords into the ventral perisome. 
Ambulacral epithelium. 
Primary interradial cords. 
Anambulacral plates. 
The secondary (radial) cords. 
Anal tube. 
Basal ring. 
First and second brachials. 
Radial blood-vessel. 
Ligaments uniting the basals to the top 
stem-joint, 
Plug of calcareous tissue in the radial 
funnel, called a rosette by Sars. 
The body-cavity or coelom. 
The bands of connective-tissue which 
traverse it. 
Fibrillar sheath round the vascular axis 
of the stem. 
Its radiating extensions. 
Coeliac canal. 
Interradial portion of the circular com- | 
missure. 
Cavities of the chambered organ. 
Their downward prolongations into the | 
stem. 
Fibres of connective tissue which traverse | J 
the fibrillar envelope of the chambered 
organ (central capsule). 
The nodal enlargements of the peripheral 
vessels of the stem (c/’). 
(zooL. CHALL. EXP,—PART XXXII.—1884.) 
cl, 
cu. . : 
Di, DeD,, 
é. 
Cirrus. 
Ciliated cups in the coeliac canal. 
Covering plates. 
Connective-tissue spaces in the perisome. 
Cirrus-vessel, 
Circumvisceral coelom. 
First, second, and fifth distichals. 
External epithelium. 
Fore-gut. 
Gut. 
Its epithelial lining. 
Genital cord. 
Genital canal. 
Genital vessel. 
Intervisceral blood-vessel. 
Intraradial portion of the circular com- 
missure. 
Arm-joint. 
Pinnule-joint. 
Interradial ligament. 
Basiradial ligament. 
Interbasal ligament. 
Dorsal ligament between the arm-joints. 
The fossa in which it is lodged. 
Interarticular ligament of the arms. 
The fossa in which it is lodged. 
Caleareous network in the perisome. 
Labial plexus. 
Its radial extensions beneath the ambu- 
lacra. 
Interarticular ligament of stem. 
Mouth, 
Muscle, 
Transverse muscle-threads in the water- 
vessels. 
Muscle-plate. 
Ti 56 
