96 GUIDE TO THE AUSTRALIAN MUSEUM. 



Sub- Kingdom IV.— ECHINODERMATA. 



The Echinodermata consist of marine animals with a radiate 

 arrangement, having usually tive rays or arms, but often more ; 

 the skin is cliarged with calcareous bodies in the form of spicules 

 or plates, occuring either as separate masses, or variously com- 

 bined so as to form a continuous skeleton, as in the sea-eggs. 



The Echinodermata are divided into five sub-classes. 



Sub-Class I.— The CRINOIDSA or Feather Stars.— This 

 sub-class is represented in the collection by Pentacrinus caput- 

 mediisa*', Antedon pumila, Actinometra Solaris, &c. The first 

 named is a stalked form which is attached to rocks on the sea 

 bottom throughout its life, whilst the two latter are stalked only 

 for a sliort time in their young state, the adult animal being 

 free-swimming. (See Case 2.) 



Sub-ClassII— The ASTEROIDEA or Star Fishes, which 

 are chietly characterised by the five-rayed star-like shape of the 

 body, the ambulacral feet being confined to the ventral surface of the 

 body, and the skeletal plates of the ambulacral area being articu- 

 lated together like vertebrae. There are four orders in this sub- 

 class : — 



1. Asteriadse, with four rows of ambulacral tube feet, 



each terminating in an expanded disc, which acts like the 

 sucking discs of the Octopus. Examples — Asterias cala- 

 maria, A. ^jolyjdax, Uniopliora glohifera, &tichaster aus- 

 tralis, Heliaster helianthus, H. microhrachia, and H. 

 kuhingii. (See Case 5.) 



2. SolasteridSB, with the ambulacral feet in two rows. 



Examples — Solaster decanus, Echinaster purpureus, LincJcia 

 pacijica, Anthenea aciUa, Pentaceros nodosns, Pentago- 

 nasier diibenii, Asterina calcar, A. exigua, and A. gunnii. 

 (See Cases 3, 4, and 5.) 



3. Astropectinidae. — In this order the ambulacral feet 



are conical and devoid of the disc-like terminal suckers. 

 Examples — Astropecten polyacantJius, A. triseriatus, Liiidia 

 inacidata^ and Archaster typicus. (See Cases 2 and 3.) 



