NO, 3 CASSIDULOID ECHINOIDS — KIER TTJ 



G. agariciformis they curve anteriorly. This difference is not of 

 sufficient significance to warrant generic distinction. 



Genus HYBOCLYPUS L, Agassiz 

 Hyboclypns L. Agassiz, 1839. £ch. foss. Suisse, vol. i, p. 75. Type species by 



monotypy, Hyboclypus gibberulus L. Agassiz. 

 Synonym: Aulacopygus Fomel, 



GENERIC DESCRIPTION 



Medium to large size, flattened ; apical system tetrabasal, elongate, 

 oculars II and IV usually in contact ; petals slightly developed, all 

 ambulacral plates double pored; periproct in contact with apical 

 system, in longitudinal groove continuing to posterior margin; peri- 

 stome anterior; no bourrelets, phyllodes double pored with many 

 pairs of pores in three rows on each side ; no buccal pores ; tubercles 

 slightly larger adorally than adapically. 



Comparison zcith other genera. — Hyhoclypus is very similar to 

 Galeropygus. In both genera the petals are slightly developed, the 

 periproct is in contact with the apical system, and the phyllodes have 

 many pore pairs arranged in three series in each half -ambulacrum. 

 It is distinguished by having an elongate apical system with oculars 

 II and IV usually separating genital plates 2 and 3 from i and 4, 

 whereas in Galeropygus the system is broad with the genital plates 

 arranged in a semicircle around the anterior margin of the periproct. 

 Furthermore, in Hyboclypus there are no bourrelets, whereas they 

 are slightly developed in Galeropygus. 



Range and distribution. — Jurassic (Bajocian to Rauracian) of 

 Europe. 



DESCRIPTION OF TYPE SPECIES 



HYBOCLYPUS GIBBERULUS L. Agassiz 

 Plate I, figures 6, 7; text figures 4, S 



Hyboclypus gibbcntlits L. Agassiz, 1839. £ch. foss. Suisse, vol. i, p. 75, pi. 12, 

 figs. 10-12. 



Material. — Two specimens studied in the Lambert Collection, at 

 the Sorbonne, i in the Museum National d'Histoire Naturelle, Paris, 

 and 17 at the British Museum (Natural History). 



Shape. — Medium to large, round to elongate, varying with speci- 

 mens, generally low except for high ridge extending from apical 

 system toward anterior margin ; depressed around peristome, inter- 

 ambulacra inflated, ambulacra depressed. 



