Proceedings of the Royal Irish Academy. 
DESCEIPTIOl^ OF THE PLATES. 
Plate XXY. 
1 . Pentagonaster halteatus, Sladen. Abactinal aspect ; natural 
size. 
2. Abactinal aspect of a ray ; magnified 3 diameters. 
3. Actinal aspect of a ray ; magnified 3 diameters. 
4. A portion of the abactinal surface ; magnified 15 diameters. 
5. Adambulacral plates and adjacent portion of the actinal sur- 
face ; magnified 27 diameters. 
Plate XXYI. 
1. Pentagonaster concinnus, Sladen. Abactinal aspect ; natural 
size. 
2. Abactinal aspect of a ray ; magnified 3 diameters. 
3. Actinal aspect of a ray ; magnified 3 diameters. 
4. A portion of the abactinal surface ; magnified 25 diameters. 
5. Adambulacral plates and adjacent portion of the actinal sur- 
face ; magnified 18 diameters. 
Plate XXYII. 
1. Pter aster per sonatus, Sladen. Abactinal aspect, natural size. 
2. Actinal aspect ; natural size. 
3. A portion of the supradorsal membrane ; magnified 6 diameters. 
4. Adambulacral plates and adjacent portion of the actinal sur- 
face ; magnified 7 diameters, 
5. Mouth -plates ; magnified 5 diameters. 
Plate XXYIII. 
1 . Symenaster giganteus, Sladen. Abactinal aspect ; natural size. 
2. A portion of the supradorsal membrane ; magnified 5 diameters. 
3. Adambulacral plates and adjacent portion of the actinal sur- 
face magnified 4 diameters. 
Plate XXIX. 
1 . Porocidaris gracilis, Sladen. Profile view ; natural size. 
2. Actinal aspect ; natural size. 
3. A portion of the test near the ambitus ; magnified 5 diameters. 
4. A portion of a primary radiole ; magnified 12 diameters. 
5. Apical system ; magnified 3 diameters. 
