PLATE LVIL 



The Lettering is the same in all the Figures. 



(ic. Ambulacral epithelium. 

 (iH. Aiiainbulacral jilate. 

 I>. KaJial blood-vessel. 



p. Pigment granules. 

 re. Rectum. 



Sinnelets on the disk. 



Connective tissue lueslnvork in the coelom. I up. Side plate. 



fp. Covering plate. 



cvc. Circumvisecral eoeloni. 



r'g. Koregut. 



(J. Epithelial lining of the gut. 



!iv. Genital ve.ssi'l. 



lb. Intervisceral blood-vessel. 



/p. Labial plexus. 



ir. Its radial extensions beneath the ambulacra 



II. Ambulacral nerve. 



sub. Subanibnlacral plate. 



T. Tentacle. 



III. Tentacular branch of water- vessel. 



If. Radial water-vessel. 



wp. Water-jjore. 



let. Water-tube. 



X. Plexiform gland. 



./ r. Its ventral end which joins the labial plexns. 



Fig. 1. Pentacrinus wyville-thomsoni, Jefireys. 



Diam. Page 



Fig. 1. Transverse section of the disk in the anal interradius, showing 

 the labial plexus (Ip) and its extensions beneath tlie am- 

 bulacra (//■), . . . . . . X 40 100 



Figs. 2 -.5. Pentacrinus decorus, Wyv. Thorns. 



Fig. 2. Vertical section through the outer j^art of the plexiform gland, 



showing its connection with the intervisceral blood-vessels, x 100 101 



Fig. o. 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, ih), and also 

 with the ventral end of the plexiform gland {.rv). The 

 section cuts the edge of the anal tube (re), but passes to 

 the right of the mouth, . . . . . x 30 97 



Fig. 4. Transverse section of an amlmlaerum near the peristome. 

 This shows the two lateral water-vessels (tv), which are 

 separated by the radial extension of tlie labial plexus {Ir), x 50 93 



Fig. 5. Portion of a vertical section through the periphery of the disk, 

 showing the intervisceral vessels on the outside of the 

 digestive canal, . . . . . , x 100 102 



