S2 PEOF. P. M. dttncan's retision op the 



Peristome large, branchial incisions well developed. Spines 



cylindrical, smootli or finely striated, often tricarinate at tlietop. 



Fossil. Oolitic : Europe and N, Africa. Cretaceous : Europe. 



Subgenus Aceopeltis, Agass. (genus), 184-0, Catal. Syst. Ectyp. 

 p. 19 ; EcJi. Foss. de la Suisse, pt. ii. p. 27. 



The primary tubercles of all the areas are imperforate and 

 uncrenulate ; the largest tubercles are actinal. 



Fossil. Oolite: Europe. 



The type of A. concinna, Merian, figured by Cotteau, 1861, 

 Eev. et Mag. de Zool. vol. xiii. p. 76, is immature, it being only 

 1 millim. high, and 2 millim. broad. Hence the large dorso-central 

 system. 



Genus GtONIoptgus, Agass. 1838, Monogr. d'EcJi. viv. et foss\ 

 livr. i. p. 19. De Loriol, 1887, Faune Gret. du Portug., Echk 

 fasc. i. p. 55. 



Test small, depressed, bemispberical dorsally, circular in out- 

 line at the tumid ambitus, broader than high. 



Apical system large and stout, the prominent basal plates 

 close, polygonal, and angular adorally or almost square ; sutures 

 dentated, perforated, or otherwise ornamented ; periproctal 

 edges in ridges and notched ; periproct small, triangular or 

 square, and may be circular in outline ; radial plates remote 

 from the periproct, pentagonal and wide actinally, variously 

 ornamented. 



Ambulacra narrow, with two vertical rows of primary plain 

 tubercles, smaller than those of the interradia, which are large, 

 plain, and in two vertical rows. Pairs of pores in simple prinaary 

 plates abactinally, but near tbe tubercles of the actinal surface 

 the plates are triple compounds, there being an adoral demi- 

 plate, a median primary, large, and an aboral primary ; the 

 sutures are convex towards the tubercle. 



Peristome very large, with small branchial incisions. Spines 

 small, club-shaped, striated or not. 



Fossil. Cretaceous : Europe, N. Africa, Asia. Eocene : 

 Europe. 



