GENEBA AITD GEOUPS OF THE ECHHSTOIDEA. 211 



rostrum, is nearly vertical, narrow, and groored. Actinally the 

 test is narrower than dorsallj, and is convex from before back- 

 wards and from side to side. 



Apical system small, on the top of the rostrum ; there are four 

 basal plates * placed closely, and the anterior pair are alone per- 

 forated by genital ducts. Radial plates small. 



Ambulacra apetalous, and, with the exception of the anterior, 

 which is in the anterior groove t, flush witii the test. Pairs of 

 pores of the anterior ambulacrum few and wide apart, continued 

 up over the end of the rostrum abactinally. Pairs of the antero- 

 lateral ambulacra small and indistinct, passing down the rostrum 

 abactinally J, and keeping close to the edge of the anterior part 

 of the test ; the posterolateral pair passing parallel to the 

 ridge of the dorsum to close to the oblique posterior edge, and 

 then passing downwards to reach the actinal surface far back, 

 and running along the convex median part on either side to the 

 excentric in front peristome. 



Peristome § at the end of the anterior groove, transversely 

 elliptical ; posterior interradium meridosternous behind the peri- 

 stome. Periproct || at the top of the posterior groove. 



Ornamentation small, scarce, made up of close miliaries. 

 Primary tubercles absent. Pascioles absent, 



Fossil. Upper Chalk : England, Europe. 



Hagenowia eostratxjs, Forbes, sp., 1852, Mem. Geol. Sur- 

 vey, Decade iv. p. 3, pi. x. 



Test compressed at the sides, with the apex produced as an 

 elongate, oblique, slender rostrum. 



Subfamily Urechinince. 



Ambulacra uniporous. 



The genus Urechinus, A. Agass., has had its solitary species 

 well studied by its first describer, and also by Loven ; but it 

 must be admitted that the shape and details of Z7, Naresi {Nare- 

 sianus, A. Ag., is probably not classical, as " Nares " refers to a man 

 and not to a place), given in the ' Challenger ' Eeport, pis, xxix., 

 XXX., XXX. a, are not those of the one species. Some forms have 

 and others have not a subanal fascicle ; and these last are. 



