ECHINOIDFA. yf 
ossicles, so that the arms can be twisted round foreign objects or 
rolled towards the mouth; the ossicles not invested by definite 
plates, but the covering-skin more or less granular. Arms simple 
or branched, arm-spines represented by papilla. Bursal clefts may 
open directly into ceelom, when true burs are wanting. No true 
teeth ; mouth-shields and oral spines present or absent. Madre- 
porite present or absent, and when present as many as five may be 
found. Pedicellaria-like processes sometimes present. Some at 
least can swim. 
Two subfamilies. 
Subfamily 1. ASTRONYCIN A. 
Astronycine, Ljungman, Uifv. Vet.-Ak. Forhlg. 1866 (1867) p. 334. 
The clefts at the sides of the arms open into burse. The arms 
undivided. Oral spines or papille present, but no oral shields. 
Madreporite single. 
One genus: Astronyx. 
Subfamily 2. GORGONOCEPHALIN A. 
Gorgonocephaline, Ljungman, Gif. Vet.-Ak. Forhlg. 1866 (1867) 
p- 335. 
The clefts at the sides of the arms open directly into the ccelom. 
The arms branch, often very considerably. Oral spines or papille 
present, but no oral shields. Madreporite single or multiple. 
One genus: Grorgonocephalus. 
Division Il. ZYGOPODA, 
Zygopoda, Bell, Ann. § Mag. viii. (1891) p. 214. 
The Zygopoda are Eleutherozoa in which the podia extend more 
or less uninterruptedly from the calycinal to the oral region. 
Class XI. ECHINOIDEA. 
Kehinus, Linn. Syst. Nat. x. (1758) p. 665. 
Echinides, Zamk. Syst. (1801) p. 345; de Bl. Dict. Sci. Nat. Ix. (1830) 
p. 178; zd. Actinol. (1834) p. 197 ; Desmoulins, Act. Soc. Linn. Bor- 
deaux, vii. (1835) p. 167. 
Oursins, Cuvier, Tab. Elém. (1798) p. 647. 
Echinoides (Echinoida), Latretlle, Fam. Nat. (1825) p. 532. 
Echinida, Macleay, Hor. Entomol. 1819, p. 3816; Gray, Ann. Phil. x. 
(1825) p. 423; id. Brit. Rad. (1848) p. 2. 
Echinide, Fvem. Brit, An. (1828) pp. 473, 474. 
