aENEEA AISTD GEOUPS OF THE ECHINOIDEA.. 237 



Fascicle peripetalous, well developed, subcircular, sloping 

 downwards and forwards, cutting across the ambulacra far above 

 the ambitus, nearly circular but slightly angular in the postero- 

 lateral interradia. Pores below the fasciole circular and similar. 



Fossil. Up]3er Cretaceous or Eocene : Europe (Spain, Erance) ; 

 Asia (Turkestan). 



Genus Agassizia, Yalenciennes, 1846, Voy. d. Venus, pi. i. fig. 2. 

 Agassiz, 1847, Ann. d. Sci. Nat. vol. viii. p. 20. LutJcen, 

 1863 (pub. 1864), Vid. Medd. f. Nat. For. i Kjdl. p. 134. 

 A. Agassiz, 1872-4, Bevision, pp. 88, 353, 594 ; 1883, 

 ' BlaTce ' Fch. p. 71, pi. 25. Loven, 1874, Etudes, pi. xxx. 

 figs. 191-193 ; 1883, Pourtalesia, pi. x. fig. 93. 



Test thin, ovoid, moderate in size, truncated posteriorly, tumid 

 and subhemispherical dorsally, highest posteriorly, without an 

 anterior groove, rather flat actinally, with a convex surface 

 behind the peristome. 



Apical system excentric or subcentral posteriorly, or not ; 

 small, with four close perforated basal plates. Madreporite in 

 the right anterior basal. 



Ambulacra diverse, the anterior in a very narrow depression ; the 

 pairs of pores small and distant, the tentacles with a sucker and 

 penicillate ; the antero-lateral ambulacra divergent, long, open, 

 slightly curved, with the anterior row of pairs of pores absent ; 

 postero-lateral shorter than the antero-lateral, closer, and with 

 both rows of pairs of pores developed. Plates 2 and 3 of zone a 

 of the right posterior interradium fused. 



Peristome very excentric in front, narrow, transverse, with a 

 posterior labrum and a well-developed amphisternum ; peri- 

 stomial plates rather large near the anterior margin. Periproct 

 elliptical, transverse, in the posterior truncation, its p]ates large 

 near the edge. 



A peripetalous fasciole entering the angles of the interradia, 

 especially posteriorly. A lateral fasciole arising from the peri- 

 petalous close to the distal ends of the antero-lateral ambulacra 

 and passing backwards to reach the posterior surface of the test 

 below the periproct. The anterior part of the peripetalous 

 fasciole dips down so as to be visible from the actinal surface. 



Spines delicate, and those of the miliaries club-shaped. Ambu- 

 lacral pedicellarise small-headed, long-stemmed, articulated at 

 the base. Tentacles, some of the anterior near the apical system 



