EXPLANATION OF THE PLATES. 135 



Fio-. 4. Same as Fig. 2, only denuded of spines to show tlie plates of the actinal surface supporting 



them. 

 Fig. 5. Longitudinal section through the median line of the ambulacral furrow. 



All Figures natural size. 



This species is generally, on the abactinul side, a dirty orange yellow, passing into red; more yellowish and lighter in 

 shade on the actin.il surftice. 



PLATE XVITL 



Cribrella sanguinolenta. 



Fi<T. 1. Seen from the abactinal side, to show the minute spines covering the whole disk and arms. 



Fif. 2. Fig. 1, seen from the actinal side. 



Fin-. 3. Enlarged view of spines round the actinostome and base of the arms. 



Fio-. 4. Actinal view ; specimen denuded of its spines to show the close system of limestone plates form- 

 ing the actinal surface. 

 Fi"-. 5- Interior view of the abactinal surface, showing its close reticulation. 



Fig. 6. Longitudinal section across the central line of the ambulacral furrow, somewhat enlarged. 



Fig. 7. Interior view of the ambulacral system of one of the arms and its central connection, somewhat 



enlarged. 



Figures 3, 6, 7 are somewhat enlarged ; all others, natural size. 



This species varies in color from brilliant orange-yellow to dark purple or dnll violet. 



PLATE XIX. 



ASTROPECTEN ARTICULATUS. 



Fig. 1. Dried specimen, from the abactinal side. 



Fig. 2. Fig. 1, seen from the actin.il side. 



Fig. 3. Abactinal view of denuded specimen. 



Fig. 4. Actinal view of denuded specimen. 



Fig. 5. Interior view of actinal floor, showing ambulacral system, the interbr.ichial arches, the connection 



of ambulacra round the actinostome. 



Fig. 6. Interior view of the abactinal surface. 



Fig. 7. Actinal region of specimen somewhat larger than Fig. 4. 



Fig. 8. Longitudinal section through arm, showing the great thickness of the marginal plates. 



All Figures are natural size. 



The marginal plates are of a light brown color with darker edges; the abactinal surface of nearly the same shade, some- 

 what lighter than the plates. The color is sometimes arranged in darker rectangular patches along the edge of the arms 

 on the abactinal side. The marginal plates are also bright yellow, enclosing a violet abactinal surface. 



PLATE XX. 



LUIDIA CLATHRATA. 



Fig. 1. Abactinal view from life. 



Fig. 2. Same, seen from the actinal side, showing the two rows of pointed tentacles. 



Fig. 3. Same view as Fig. 1, denuded specimen. 



Fig. 4. Preparation showing the plates of the actinal surface. 



Fig. 5. Interior view of actinal floor, showing ambulacral system and mode of connection round actinal 



opening. 

 Fig. G. Interior view of abactinal surface. 

 Fig. 7. Actinal view of central part of disk, with tentacles contracted, showing the spines along the edge 



of ambulacral furrows and at their junction. 

 Fig. 8. Longitudin.al section of aim. 



