EXPLANATION OF THE PLATES. 131 



moutli, 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 abac- 



tinal area, and the Echinus-like arrangement of the spines in the young Starfish. The odd 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 the 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. 

 Fio'. 8. A "reatly masfnified fisjure of a full-<rrown Brachiolaria in its natural attitude, at rest, with the 



Starfish almost ready to resorb the larva; the obliquity of tlie 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 VI.II. 



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



Figs. 2-4. Magnified views of spines (;>), and of rudimentary pedicellaria; (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 ((/') at the angle of the rays. 

 Fig. 7. One of tlie abactinal water-tubes {<t") along the edge of the rays. 

 Fig. 8. Abactinal view of the arm of a young Starfish, probalily two years old. 

 Fig. 9. Actinal view of an arm of a young Starfish in its third year. 

 Fig. 10. Abactinal view of a young Starfish, in which the rudimentary pedicellarise have made their 



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



three years old. 



PLATE IX. 



Asteracanthion berylinus. 



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, sliowing the alternating arrangement of the ambulacral pores penetrat- 

 ing between the ambulacral plates. 



(a") Base of interbracliial 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 by soldering of the imbricating pieces attached to the interam- 

 bulacral plates. 

 Fig. 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 Asteri.is, varies greatly; it ranges from dark chocolate (on 

 the abactin.il side) to light violet. The actinal side is of a much paler shade of 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 

 pedicellariae clustered around the spines. 



