Plate 2. 



1-3. Podophora atrata Agass. 



1-3. Cystacanths from the abactinal side of a specimen 65 mm. in diameter, including 

 the spines. 



1. From the left posterior ambulacrum, near the ocular plate, front view, 0.37 mm. 



2. In the same ambulacrum, but less expanded, 0.39 mm. 



3. Profile, from the same ambulacrum, 0.29 mm. 



4-7. Colobocentrctus Stimpsoni A. Ag. 

 4-7. Cystacanths from a specimen of 88 mm. diameter with spines. 



4. Shows the attachment of the spine to the third lobe, 0.94 mm. from the left anterior 



ambulacrum, actinal side. 



5. Front view of a cystacanth 0.60 mm. from the right anterior ambulacrum. 



6. Same view of a cystacanth 0.58 mm. from the left posterior ambulacrum. 



7. Profile of a cystacanth 0.70 mm. near the ambitus, from the right posterior ambula- 



crum. 



8-13. ColobocentrotuB Mertensii Brandt. 



8-13. Cystacanths from a specimen 70 mm. in diameter including spines. 



8. Contracted, with spine, 1.15 mm. close to the ambitus, from the odd anterior ambula- 



crum. 



9. Rear view, 0.44 mm. from the left anterior ambulacrum. 



10. Seen from beneath, 0.59 mm. near the ambitus, from the left anterior ambulacrum. 



11. Spine of a cystacanth. 



12. Upper end of same, somewhat more magnified. 



13. Spine of a pedicellaria. 



All the figures are equally magnified; measurements indicate the natural size of the sacs 

 without spine. 



