180 



OOLITIC ECHINODERMATA. 



the apex, two meeting at the summit, and three nearer the anal opening. Poriferous 

 zones narrow, continuous ; pores unigeminal. Interanibulacral areas covered with small 

 perforated and crenulated tubercles. Oral opening small, obtusely pentagonal, excentric. 

 Jaws absent. Anal opening small, oval in the middle of non-sulcated margin. Genus found 

 in the Oolitic and Cretaceous strata. Three British Oolitic species (Vol. I, 309 — 318). 



Pamilt VIIL— ECHINOBRISSIDtE, JFrigJd (Vol. T, p. 330). 



Test thin, oblong, subpentagonal, circular, covered uniformly with small uncrenu- 

 lated imperforate tubercles, largest on the under side. Ambulacral areas narrow and 

 petaloid, lanceolate above, expanded in the middle, contracted and open below. Pori- 

 ferous zones at the border and base narrow ; pores small, equal. Interambulacra wide. 

 Apical disc small. Oral opening small, subcentral, and pentagonal, sometimes lobed. 

 Jaws absent. Anal opening large, placed in a furrow on the upper surface or at the 

 margin. The Echinobrissidae range from the OoHtic to the existing period. Two 

 British Oolitic genera (Echinobrissus and Clypeus), and sixteen species. 



Genus 19. — Echinobrissus, Breynius (Vol. I, p. 331). 



Test thin, small, oval or subcircular, convex above, subconcave below, rounded in 

 front, truncated, and generally widest behind ; marked by small tubercles, which are 

 larger on the under surface than on the upper. Ambulacral areas petaloid on upper 

 surface, straight on lowei'. Oral opening small, excentric. Peristome pentagonal or 

 oblique. Jaws absent. Anal opening circular, on upper surface, in a sulcus sometimes 

 extending the whole distance, sometimes only a part, from the apical disc to the border 

 of under side. Apical disc small,, square, compact. Genus ranges from the Oolitic to 

 the existing period. Eight British OoHtic species (Vol. I, pp. 332 — 353). 



Genus 20.— Clypeus, Klein (Vol. I, p. 360). 



Test large, discoidal ; upper surface moderately subconvex, depressed ; under surface 

 flat, concave, undulated. Ambulacra petaloid on upper surface, straight on under surface. 

 Oral opening central or subcentral, small, lodged in a depression. Peristome lobed. 

 Jaws absent. Anal opening oval or pyriform, situated in a sulcus extending wholly or 

 partially from the apical disc to the lower border. The genera is found in the Oolitic 

 strata. Eight British Oolitic species (Vol. I, pp. 361—382, 466). 



