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PLATE XVII. 
Fig. 1. PENTACRINUS MACLEARANUS, Wyv. Thoms. 
. Arm-groove of Pentacrinus maclearanus,  . ‘ 
Figs. 2-6. PENTACRINUS WYVILLE-THOMSONI, Jeffreys. 
. Ambulacral skeleton of a pinnule ; from the side, 
. The same, near the base of the pinnule ; from above, 
. The arm-groove and brachial ambulacrum, 
. Vertical section of a decalcified specimen. Much of the alimen- 
tary epithelium has fallen away. The lobulated organ to 
the right of the centre of the figure is the plexiform gland, 
The disk of a dry specimen, . 
Figs. 7, 8. Penracrinus AsTeRtus, Linn, sp. 
Ventral aspect of one of the lower arm-divisions, showing the 
ambulacral skeleton, 
. The arm-groove and brachial ambulacrum, 
Figs. 9, 10. Penracrinus MULLERI, Oersted. 
. The arm-groove and brachial ambulacrum, 
. The disk of a spirit-specimen, 
Diam. 
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