394 



AsTEEIID,E.- 



-RADIATA.- 



-OrHIOKID.E. 



power of reproducing lost parts when accidetitally de- 

 stroyed. If an entire arm be torn off, provided a small 

 portion of the body remains attached to it, other arms 

 are reproduced, and a fresh, perfect animal is formed. 

 In each ray we find two ovaries, and it is supposed that 

 the animals can reproduce their species without the aid 

 of a second individual. The spawn is said to be veno- 

 mous to the touch, and poisonous to the animals which 

 eat them. The larva?, or young, are very different in 

 appearance from the adult animal. They are ciliated, 

 and move with great quickness by means of their vibra- 

 tile cilia, and swim rapidly, rotating round their axis. 

 The order Asteroidca is rather an extensive one, com- 

 prising numerous species and many genera, which may 

 be arranged in five Families: — I. Anteriidm; II. Astro- 

 pcdeiiidfE; III. Pentacerotidcn ; IV. Asterinida: ; and 

 V. Ophiurida:. 



Family I.— ASTEKIIDiE [True Sea-stars). 



In this family, the typical Star-fishes, the rays are 

 five in number, and they much exceed in length the 

 diameter of their disc. The family is represented on 

 Plate G, fig. 2., by A. cylindrlca. 



Family II.— ASTROPECTENID^ {Aslropcdcns). 



In this family the back of the rays or arms, which 

 are various in number, are thin and netted, and have 



F.;;. 215. 



the coast of England, Aslropcctcn irrcgidaris, the 

 " Asterias aurantiaca" of Muller, and by the Solasler 

 pcippnsus, the Rosy Sun-star or Ten-fingers — see fig. 

 235 — which, as this latter name indicates, possesses 

 ten rays, that nearly equal in length the diameter of 

 the disc. 



Family III.— PENTACEROTIDiE. 



This family is characterized by the body being 

 formed of large roundish tubercles, the skin between 

 which is pierced with small holes. The genera into 

 which the members of this family have been divided, 

 are rather numerous. Many of the species have their 

 backs studded with conical tubercles, which enlarge in 

 size as the part on which they are placed increases. 

 These tubercles sometimes fall off as the animal be- 

 comes larger, and are easily separated, leaving a flat 

 scar when the animal is dead. — (Gray.) 



This family is represented in Plate 6, fig. 3, by 

 Penkigonasier puhhellus, a species which is found in 

 the Indian seas. 



Family IV.— ASTERINIDJ3 {The Birds'- 

 foot Stars). 



This, the last family of the Asteroidca, have the body 

 formed of compressed pieces, placed one over the other 

 like the tiles on a house. They are generally thin, 

 flat, and pentangular, have always a thin 

 margin, and are covered above and beneath 

 whh fasciculated spines. Some of the 

 species have the back convex, and a few 

 are possessed of many rays. 



Family V.— OPHIURIDA {Lizard- 

 tailed Star-fishes). 







Solaster p.ipposus. 



numerous tubercles at the junction of each of the little 

 bones, which are covered at their tips with many small 

 movable spines. Tliey are very beautiful creatures. 

 Tlie family is well represented by a species found on 



This fiimily of Echinoderms is char- 

 acterized by the species having a more 

 or less orbicular, depressed body, with 

 five cylindrical, jointed, very flexible arms, 

 which are sometimes very long, and re- 

 peatedly divided into branches. Their 

 arms are furnished with a series of small 

 pores along each side of the under sur- 

 face, and they have a lunate hole on each 

 side of the base of their arms. They 

 are scaly, like the tails of serpents or 

 lizards, and are very fragile ; hence their 

 common English name. They are desti- 

 tute of grooves or gutters underneath, 

 and have in consequence no tentacles. 

 Their motion, therefore, is different from 

 that of the true Star-fishes. When they 

 move, the animals employ the two arms 

 nearest the point to which they wish to 

 go, and the one farthest from it. The 

 two first, curving at the extremities, form 

 two hooks directed outwardly, which applying them- 

 selves to the sand, draw the body forwards; whilst 

 the posterior arm is curved vertically, and pushes the 

 animal along. The species of Lizard^tails live exclu- 



