Fig. 
ny A 
Fig. 
Fig. 
IL 
PLATE LVI. 
The Lettering is the same in all the Figures. 
we. Ambulacral epithelium. 
an. Anambulacral plate. 
6. Radial blood-vessel. 
c. Connective tissue meshwork in the coelom. 
cp. Covering plate. 
eve. Cireumvisceral coelom. 
fg. Fore-gut. 
g. Epithelial lining of the gut. 
gv. Genital vessel. 
ib. Intervisceral blood-vessel. 
p. Labial plexus. 
lr. Its radial extensions beneath the ambulacra. 
n. Ambulacral nerve. 
p. 
Te. 
Pigment granules. 
Rectum. 
Spinelets on the disk. 
. Side plate. 
. Subambulacral plate. 
. Tentacle. 
. Tentacular branch of water-vessel. 
. Radial water-vessel. 
. Water-pore. 
Water-tube. 
. Plexiform gland. 
rv. Its ventral end which joins the labial plexus. 
Fig. 1. PENTACRINUS WYVILLE-THOMSONI, Jeffreys. 
Transverse section of the disk in the anal interradius, showing 
the labial plexus (Jp) and its extensions beneath the am- 
bulaera (Ur), 
Figs. 2-5. Prnracrinus pEcorus, Wyv. Thoms. 
Vertical section through the outer part of the plexiform gland, 
showing its connection with the intervisceral blood-vessels, — x 
The upper part of a longitudinal vertical section through the 
disk, showing the connection of the labial plexus (/p) with 
the genital and intervisceral vessels (gv, 7b), and also 
with the ventral end of the plexiform gland (av). 
section cuts the edge of the anal tube (re), but passes to 
the right of the mouth, 
Diam. 
x 40 
100 
The 
x 30 
Transverse section of an ambulacrum near the peristome. 
This shows the two lateral water-vessels (w), which are 
separated by the radial extension of the labial plexus (Ir), x 50 
. Portion of a vertical section through the periphery of the disk, 
showing the intervisceral vessels on the outside of the 
digestive canal, 
2 a eeOO 
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