Fig. 1. Portion of an oblique section through an arm-joint and the 
base of a pinnule, . ; : : : 
Fig. 2. Transverse section of an arm-joint with attached pinnule, 
Fig. 3. Portion of a nearly longitudinal section of a pinnule, . 
Figs. 4-10. HyocrInus BETHELLIANUS, Wyv. Thoms. 
Fig. 4. Terminal face of a stem-joint, 
Fig. 5. Optical section of a piece of stem cut longitudinally, . 
Fig. 6. Portion of the disk, showing one oral plate and the anambu- 
lacral plates lying outside it, 
Fig. 7. Transverse section of a pinnule, 
Fig. 8. Terminal portion of a pinnule, mounted in dammar and seen 
in optical section, . 
Fig. 9. Portion of a dry pinnule about the end of the enlargement to 
receive the genital gland, . : : : 
Fig. 10. Lower portion of a pinnule, mounted in dammar and seen in 
PLATE Ve. 
The Lettering is the same in all the Figures. 
A, Axial cord of arm. Js. Interarticular ligament of stem. 
a. Axial cord of pinuule. m. Muscle. 
ae. Ambulacral epithelium. O. Oral plate. 
an. Anambulacral plate. ov. Ovary. 
C. Coelom. 7s. Radial space in stem. 
ca. Fibrillar sheath round vascular axis of stem. sp. Side plate. 
cc. Coeliac canal. , ste. Subtentacular canal. 
cic, Ciliated cup. T. Tentacle. 
cp. Covering plate. t. Testis. 
ge. Genital cord. v. Central vascular axis of stem. 
J, Arm-joint. w. Radial water-vessel. 
j. Pinnule-joint. wp. Water-pore. 
ld. Dorsal ligament. 
Figs. 1-3. Hoxopus rani, d’Orbigny. 
optical section, . : , . : 
Diam. 
<a 
<0 
St) 
x 20 
ee ARS 
<< 20 
x 80 
eS) 
a 2, 
<6 
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