182 OOLITIC ECHINODERMATA. 



The Asteroidea range from the Cambrian formation to the existing period, and are 

 represented in the British Liassic and Oolitic strata by two sections (A and B), four famiKes 

 UrasteridtE, Tropidasterid^, GoNiASTERiDiE, and AsTROPECTiNiD^j, eight genera 

 (Uraster, Tropidaster, SoiiASTER, GoNiASTER, Stellaster, Luidia, Plumaster, and 

 Astropecten), and twenty-three species. 



Section A. — Four rows of pores in each amhulacral space. 



The section is represented in the British Liassic and Oolitic strata by one family 

 (Urasterid^) and three species. 



Family X.— URASTERIDtE, Wright (Vol. II, p. ii). 



Body stellate, rays long, rows of spines near the ambulacral areas on the under side. 

 Upper surface of body and rays covered with blunt or pointed spines, either scattered, 

 grouped, or linearly arranged. Integument between the spines naked. Pour rows of pores 

 in each ambulacral space. Pedicellariae on soft stems. Anal opening subceutral. Range of 

 the family from the Lias to the existing period. Pamily represented in the British Liassic 

 and Oolitic strata by one genus (Uraster) and three species 



Genus 22. — Uraster, Agassiz (Vol. II, p. 99). 



Body stellate, rays five, moderately long, cylindrical or lanceolate, deeply cleft on 

 under side, fringed below with rows of small and laterally with larger spines. Skeleton 

 composed of small irregularly shaped and femur- like ossicula, articulated together in a 

 retiform manner. Upper surface of body studded with blunt or pointed spines, scattered 

 or grouped together in tufts, and arranged more or less regularly in longitudinal rows. 

 Ambulacral avenues wide, composed internally of two rows of long femur-like bones, 

 spaced for the admission of four series of tentacula. Anal opening small, subcentral. 

 Madreporiform body simple. Range of the genus from the Lias to the existing period. 

 Three British Liassic and Oolitic species (Vol. II, pp. 100, 101, 166). 



Section B. — Two rows of pores in each ambulacral space. 



The section is represented in the British Liassic and Oolitic strata by three families 

 (TROPiDASTERiDiE, GoNiASTERiD^, and AsTROPECTiNiD^), scvcu genera (Tropidaster, 

 Solaster, Goniaster, Stellaster, Luidia, Plumaster, and Astropecten), and twenty 

 species. 



