756 ON THE ECHINOIDEA OF THE ‘PORCUPINE’ EXPEDITIONS. 
Fig. 3. Inner aspect of the anterior portion of the test, showing the mouth, the oral ring 
of the ambulacral vascular system, the ambulacral vessels of the trivium, and 
the disjunct apical system. X 2. 
Fig. 4. The mouth from within, showing the ring of the ambulacral vascular system 
and the mode of origin of the five ambulacral vessels, x 4. 
Fig. 5. Lateral view of the oral inversion of the test, seen from within. X 4. 
Fig. 6. Inner aspect of the posterior portion of the test, seen from below. X 2. 
Fig. 7. Anal opening, and the arrangement of the plates and scales of the periproct, 
from within. X 4. 
Fig. 8. The looping of the vessels of the bivium opposite the anal opening. 
Fig. 9. A portion of a spine. 
