1S6 
OOLITIC ECHINODERMATA. 
side in one of the buccal plates placed near the oral opening. No pedicellarise. Move- 
ment (in the living state) effected by the rays. 
The Ophiuroidea range from the Silurian formation to the existing period, and are 
represented in the British Liassic and Oolitic strata by one family (Ophiuiiid^e), five genera 
Ophioderma, Ophiolepis, Acroura, Amphiura, and Ophiurella), and twelve species; 
and are divisible into three sections (A, B, C), dependent upon the number of genital 
fissures and the nature of disc. 
Family XIV.— OPHIURID^, Wric/Jd (Vol. II, p. 138). 
Body discoidal, depressed, having long slender rays ; disc covered with hard plates, 
or membranous and naked. Two or four fissures {genital) in under side of disc in the 
area bounded by the rays and margin of mouth {interhracMal space). Rays five, always 
simple. Range from the Silurian to the existing period. 
Section A. — Four genital fissures in each interirachial space. 
The section is represented in the British Liassic strata by one genus, Ophioderma, 
and five species. 
Genus 30. — Ophioderma, Milller and TroscJiel (Vol. II, p. 140). 
Disc and arms smooth, covered with small closely set granules. Arms long and 
slender ; lateral borders provided with short papillae or fine spines. Four genital fissures, 
disposed in pairs in radial lines. Range of the genus from the Liassic to existing period. 
Five British Liassic species (Vol. II, pp. 140 — 149). 
Section B. — Two genital fissures in each interhracMal space. Disc provided loith plates. 
The section, ranging from the Trias to the existing period, is represented in the British 
Oolitic strata by three genera (Ophiolepis, Acroura, and Amphiura) and five species. 
Genus 31. — Ophiolepis, Milller and Troschel (Vol. II, p. 150). 
Disc provided with naked scales or shields on its upper surface. Two genital fissures 
close to the arms. Oral opening bordered with a single row of hard papilla. Oral 
plates simple and heart-shaped. Lateral borders of arms bearing papillae or spines. 
