SUMMARY. 349 



above, wide below, with two perfect and sometimes two imperfect rows of prominent 

 creimlated and imperforate primary tubercles ; the two perfect rows close together at the 

 peristome and wide apart at the anal opening. Primary tubercles of the same size in 

 both areas. Poriferous zones well developed, straight on upper side, undulating at the 

 ambitus and base ; poriferous plates unequal and irregular. Pores unigeminal, more 

 or less bigeminal on upper surface and crowded together at the peristome. Oral opening 

 large, subcircular, incised and lobed. Anal opening large, pentagonal, the angles 

 extending into the middle portion of the interambulacra. Elements of anal disc feebly 

 united. Spines long, solid, of moderate thickness, cylindrical, aciculate, spatuliform or 

 spoon -shaped. The genus confined to the Cretaceous strata. Seven British Cretaceous 

 species (pp. 129 — 144. 



Family III.— SALENIAD^, Wright, (p. 144). 



Test thin, small, spheroidal, hemispherical or depressed. Ambulacral areas wide or 

 narrow, straight or flexuous, furnished with two rows of secondary tubercles alternating 

 with each other on the margins of the area. Interambulacral areas wide, having two 

 rows of primary, crenulated tubercles perforate or imperforate. Poriferous zones narrow. 

 Pores unigeminal, except near the peristome where they fall into oblique rows of three. 

 Oral opening sometimes small, sometimes large, more or less decagonal, deeply or feebly 

 indented. Anal opening sometimes small. Apical disc large or small, pentagonal or 

 undulated, much developed, carrying a suranal plate in the middle of the disc, consisting 

 of one to eight separate elements. Periprocte excentric. Spines long, slender, straight, 

 curved, angular or flattened, ovoid or subglandiform. Eamily ranging from the Jurassic 

 to the existing period, and represented in the British Cretaceous strata by four genera : 

 Peltastes, Goniophorus, Salenia, Cottaldia, in eighteen species (pp. 149 — 189). 



Genus 7. — Peltastes, Agassiz (p. 149). 



Test thin, small, circular, more or less inflated above, almost flat below. Ambulacral 

 areas narrow, straight, or slightly flexuous, furnished with two rows of small, close-set, 

 alternating secondary imperforate tubercles. Interambulacra large, [irovided with two 

 rows of large crenulated, imperforate tubercles. Poriferous zones narrow. Pores 

 unigeminal, crowded near the peristome. Oral opening moderate in size. Peristome 

 slightly incised, unequally lobed. Apical disc generally large and solid, projecting 

 above the surface, marked by impressions and striae, shield shaped, composed of lar^e 

 plates more or less undulated at the border. The right antero-lateral ovarial provided 

 with an oblong fissure always directed from right to left and corresponding to the 



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