184 



OOLITIC ECHINODERMATA 



Gems 25. — Goniaster, Agassiz (Vol. II, p. 106). 



Body pentagonal, only slightly produced, flattened on both sides. Margins bounded 

 by two rows of granulated plates, always larger than the remaining ossicula. Two 

 rows of ambulacral pores. Range of genus from Lias to existing period. Two British 

 Oolitic species (Vol II, pp. 108, 109). 



Gems 26. — Stellaster, Gray (Vol. II, p. 164). 



Body pentagonal, angles produced, rays tapering. Marginal plates thick, finely 

 granulated. Lower marginal plates bearing spines and granules. Upper and under 

 surfaces, apart from the marginal plates, covered with small polygonal ossicles, smooth 

 and granulated. Ambulacral furrows narrow, with two rows of ambulacral pores. Anal 

 opening subcentral. Range of genus from the Oolitic to the existing period. One 

 British Oolitic species (Vol. II, pp. 165, 166). 



Family XIIL— ASTROPECTINIDiE, MuHer and TroscM (Vol. II, p. 110). 



Body stellate, flattened on both sides, rays five or numerous, narrow, elongate, and 

 bordered, sometimes by an upper and sometimes by an upper and an under series of 

 large conspicuous plates. Lower marginal plates always spiniferous ; upper, when 

 present, granulated and spiniferous to a greater or less degree. Upper surface, apart 

 from the marginal plates, covered with closely-set paxilte ; under surface crowded with 

 short spines arranged in regular rows. Ambulacral furrows narrow. Two rows of 

 ambulacral pores. Separate anal opening absent. Family ranging from the Lias to the 

 existing period. Represented in the British Liassic and Oolitic strata by three genera 

 (LuiDiA, Plumaster, and Astropecten) and fifteen species. 



Genus 27. — Luidia, Forbes (Vol. II, p. 110). 



Body stellate, covered on upper surface with paxillse ; disc comparatively small ; 

 rays variable in number, sometimes numerous, elongate, provided on under surface with 

 a single row of marginal plates, carrying at the central portion short thick spines, and at 

 the margin long recurved spines. Ambulacral furrow narrow. Two rows of ambulacral 

 pores. Range of genus from the Lias to recent period. One British Liassic species 

 (Vol. II, p. 111). 



