EXPLANATIOX OF THE PLATES. 131 



mouth, limited by the limestone deposit, takes the shape of a pentagonal opening ; the ambulacral 



tube is concealed. 

 Fig. 2. The same Starfish as PI. VI. Fig. 11, seen in profile, to show the great development of the abae- 



tinal area, and the Echinus-like arrangement of the spines in the young Starfish. 'l"he o<ld tentacle 



is seen turned up, between two of the spines, with the eye at its base. 

 Figs. 3-5. Spines of the young Starfish in different stages of growth. 

 Fig. 6. An enlarged view of the terminal tentacle, to show .he position of the eye at the base of the odd 



tentacle. 

 Fig. 7. An enlarged view of the meshwork of limestone cells, to show the mode of formation of additional 



cells, by means of Y-shaped rods. 

 Fig. 8. A greatly magnified figure of a full-grown Brachiolaria in it.s natural attitude, at rest, with the 



Starfish almost ready to resorb the larva; the obliquity of the planes, in which the actinal and abac- 



tinal pentagons are situated, is especially well seen in the pointed anal extremity of this Brachiolaria. 



No letters have been added to this figure, as the different parts can readily be distinguished by com- 

 paring it with PI. IV. Figs. 1, 2, 4. 



PLATE VIII. 



Fig. 1. Young Asteracanthion about one year old, seen from the abactinal side. 



Figs. 2-4. Magnified views of spines (/)), and of rudimentary pedicellariae (/>', p"). 



Fig. 5. Odd terminal tentacle of a Starfish in the stage of PI. VIII. Fig. 10, at the extremity of the arm 



with the eye-speck (e). 

 Fig. 6. One of the abactinal water-tubes {d') at the angle of the rays. 



One of the abactinal water-tubes (r/") along the edge of the rays. 

 Abactinal view of the arai of a young Starfish, probably two years old. 

 Actinal view of an arm of a young Starfish in its third year. 

 Abactinal view of a young Starfish, in which the rudimentary pedicellariae have made their 

 appearance, also having median and lateral lines of abactinal water-tubes along the arm. Probably 

 three years old. 



PLATE IX. 



Asteracanthion berylincs. 



Fig. 1. Living specimen, seen from the actinal side. 



Fig. 2. Living specimen, seen from the abactinal side. 



Fig. 3. Preparation showing the calcareous network, abactinal side. 



Fig. 4. Abactinal calcareous network seen from the interior. 



Fig. 5. Preparation showing the connection of the solid parts, seen from the actinal side. 



(a i) Interambulacral plates, with two rows of pores at base. 



(a') Ambulacral plates, showing the alternating an-angement of the ambulacral pores penetrat- 

 ing between the ambulacral plates. 



(a") Base of interbrachial partition. 



(c) Ambulacral groove. 



{I) Lateral imbricating pieces forming the calcareous network of the abactinal surface. 

 Fig. 6. The same, seen from the interior. Lettering as in Fig. 5. 



(c) Dorsal groove of ambulacral system. 



(ip) Interradial partition formed hy soldering of the imbricating pieces attached to the interam- 

 bulacral plates. 

 Fif'. 7. Longitudinal section of preparation of arm, to show the formation of the interradial partition by 

 the soldering of the imbricating lateral pieces of the interambulacral plates. 



All Figures natural size. 



The color of this species, as of all the species of the genus Asterias, varies greatly; it ranges from dark chocolate (on 

 the abactinal side) to light violet. The actinal side is of a much paler shade )f the same color. The general tint of the 

 abactinal side depends also greatly upon the state of expansion of the water-tubes and the development of the light-colored 

 pedicellariaj clustered around the spines. 



