DIADEMAD^.. 81 



1. Famili/ — Cidarid^. Cidurites, Lamarck. 



Body with spines of two sizes; larger ones either club-shaped or very long; spine- 

 bearing tnbercles perforated at the summit. 



Genus 1 — Cidaris, Klein, Lamarck. (Les Turbans.) 



Body depressed, spheroidal ; ambulacra waved ; small spines compressed, two-edged, 

 two-rowed, covering the ambulacra, and surrounding the base of the larger spines. 



This genus may be divided according to the form of the larger spines : the extra- 

 ambulacral beads have only two rows of spines. 



Cidaris impekialis, Lamh. Klein., Nat. dispositio Echinodermatum, tab. vii, fig. a. 



Genus 2 — Diadema, Gray. (Les Diademes.) 

 Body orbicular, rather depressed ; ambulacra straight ; spines often fistulous. 



EcHiNOMETKA SETOSA, Rumph. Leske, Klein., Nat. disp. Ecbinid., tab. .xxxvii, fig. 1, 2. 

 Echinus diadema, Linn. Syst. Nat., by Turton, vol. iv, p. 139. 

 — CALAMAEIA, Pallas. Spicil. ZooL, tab. ii, fig. 4 — 8. 



Genus 3 — AsTRorvGA, Grai/. 



Body orbicular, very much depressed ; ambulacra straight ; ovarial scales very long, 

 lanceolate ; beads with several series of spines. 



Cidaris uadiata, Leske, apud Klein, tab. xliv, fig. 1. 



The veiy meager characteristics by which Dr. Gray has defined the last two genera 

 merely shows that a difference exists, and his description is insufficient for a correct dia- 

 gnosis of either ; hence the various opinions extant regarding the character and limits of his 

 genus Diadema; only one of the species enumerated as types, Diadema setosa, Rumph., 



11 



