132 • EXPLANATION OF THE PLATES. 



PLATE X. 



ECHINASTEB 8ENTUS. 



Fig. 1. Living specimen seen from actinal side. 



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

 Same from the abactinal side. 



Water-tubes of part of abactinal surface. 



IVIadreporic body. 

 Calcareous network of abactinal side. 

 Intf;rnal view of abactinal surface. 

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

 Inner view of actinal calcareous network. 



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



The color of this species varies from a dark reddish-brown to a pale violet, sometimes more or less yellowish-brown or 

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



PLATE XL 

 Aster IAS ochracea. 



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



J'ig. 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 interara- 



bulacral plates, and the adjoining actinal limestone network. 

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



support of the limestone work adjoining the interambulacral plates. 

 Fig. 6. J'ortion 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-j)lates forming the median groove on top. 

 Fig. 7. Profile view of a similar portion of the arm (as Fig. 6) 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. 



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

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

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

 invariably of a lighter tint than the ground-color. 



PLATE XII. 

 Crossaster papposus. 



l"ig. 1 . Scon from the actinal side, with the spines of the intorbrachial surface, and of the lower surface 

 of the arms. (The abactinal su'-face has been removed.) 



I'ig. 2. Seen from the actinal .^ide, with the spines removed to show the structure of the plates carrying 

 the spinas alon'i the ed;j:e of tlie arms, round- the actinostome. and of the limestone plates strengthen- 

 ing the interbrailiial membrane; tlie limestone network of the inner surface of the abactinal surface 

 is .seen throujih the opening of the actinostome. 



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

 tending as a division wall between arms, and forming the sup,>ort as well as the connection Ix'tween 

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

 plates only at its ouli-r and inner extremities, where it connects by more numerous and stronger 

 l)lales the two surfaces of the interbrachial space. The plates near the actinostome are fnxiuently 

 ilrawa out into u long comma-shaped support on the abactinil part of the connecting membrane. 



