132 EXPLANATION OF THE PLATES. 



PLATE X. 



ECHINASTER SENTUS. 



Fig. 1. Living specimen seen from actinal side. 



Fig. 1'. Portion of arm of Fig. 1, somewhat more magnified. 



Fig. 2. Same from the abactinal side. 



Fig. 2'. AVater-tubes of part of abactinal surface. 



Fig. 2". Madreporic body. 



Fig. 3. Calcareous network of abactinal side. 



Fig. 4. Internal view of abactinal surface. 



Fig. 5. Calcareous network of actinal side (same as Fig. 3). 



Fig. 6. Inner view of actinal calcareous network. 



All Figures natural size, except Figs. 1', 2', 2", which are somewhat enlarged. 



Tlie color of tliis species varies from a dark reildish-brown to a pale violet, sometimes more or less yellowish-brown or 

 purple. The water-tubes are light pink or violet. 



PLATE XI. 



ASTERIAS OCHRACEA. 



Fig. 1. Single arm and disk, seen from the abactinal side. 



Fig. 2. Single arm, seen from the abactinal side, with the spines of the limestone network removed. 



Fig. 3. Interior view of limestone network. 



Fig. 4. Actinal view of the disk and arm, to show the narrow ambulacral plates, the marginal interam- 



bulacral plates, and the adjoining actinal limestone network. 

 Fig. 5. Inner view of the same, showing the liuge spaces left between the pillars forming the marginal 



support of the limestone work adjoining the interambulacral plates. 

 Fig. 6. Portion of half of the arm, to show the arrangement of the ambulacral and interambulacral plates, 



seen from the actinal side near the base of the arm-plates forming the median groove on top. 

 Fig. 7. Profile view of a similar portion of the arm (as Fig. G) toward the central part of the arm, seen 



from the interior of the arm. 



All Figures natural size, except Figs. 6 and 7, which are somewhat magnified. 



This is often a very brilliantly colored species. Brandt has separated as species the extreme variations in color. The 

 most common coloring is a dark orange, passing in some specimens to an almost pure yellow, or in the other direction to 

 a rich chocolate color. We find also frequently violet as the prevailing tint. The ridges, on the abactinal network, are 

 invariablv of a ligliter tint than the ground-color. 



PLATE XII. 



Cbossaster papposus. 



Fig. 1. Seen from the actinal side, with the spines of the interbrachial surface, and of the lower surface 

 of the arms. (The abactinal surface has been removed.) 



Fig. 2. Seen from the actinal side, with the spines removed to show the structure of the plates carrying 

 the spines along tlie edge of the arms, round the actinostome, and of the limestone plates strengthen- 

 ing the interbrachial membrane ; the limestone network of the inner surface of the abactinal surface 

 is seen through the opening of the actinostome. 



Fig. 3. Fig. 1, seen from the interior (from the abactinal side), showing the portion of the membrane ex- 

 tending as a division wall between arms, and forming the support as well as the connection between 

 the actinal and abactinal surfaces ; this membrane is often a mere film strengthened with limestone 

 plates only at its outer and inner e.^tremities, where it connects by more numerous and stronger 

 plates the two surfaces of the interbrachial space. The plates near the actinostome are frequently 

 drawn out into a long comma-shaped support on the abactinal part of the connecting membrane. 



