GENEEA AND GROUPS OF THE ECHINOIDEA. 91 



between this arrangement and ttat already noticed is that in the 

 instance of tlie plates with more than three pairs of pores the 

 adoral primary is added, as it were, to the compound. 



The interradia liave only two vertical rows of primary tubercles, 

 very slightly lai'ger than those of the ambulacra ; and there are 

 two vertical rows of small secondary tubercles. 



Micropsis Leymerii, Cott., and M. d' Orbiffnii, Cott., appear to 

 be associated with this Sindian species in a little group which is 

 hardly worthy of more than a subgeneric title (see Gagaria). 



A new genus or subgenus is required for M. Vidali, Cott. ; for as 

 we define the species it is a PsammecMnus with crenulate tubercles. 



Having made these necessary remarks, we proceed to give 

 the diagnosis of Micropsis, which is transitional between the 

 Cyphosomatidae and the Diaderaatidse. 



Genus Miceopsis, Gotteau, 1855, Ech. Foss. des Pyren., Bull. Soc. 

 Geol. de France, ser. 2, vol. xiii. p. 326 ; 1882, Bull. Soc. Zool. 

 de France, vol. vii. p. 411. Buncan and Sladen, 1884, Pal. 

 Ind. ser. siv., Foss. Fch. of Sind, p. 119. {Amended.) 



Test of variable size, circular or slightly polygonal in tumid 

 marginal outline, tumid dorsally, subconical, subhemispherical 

 or depressed, concave actinally. 



Apical system flush, with a large periproct, large basals, and 

 one or more of the radial plates may or may not enter the ring. 

 Coronal plates rather numerous. 



Ambulacra with small primary tubercles, perforated and cre- 

 nulated, in two or more vertical rows ; pairs of pores from three 

 to five in number ; plates compound ; theaboral components low 

 and broad, with adoral sutures convex adorally, and the adoral 

 component a large primary carrying the tubercle ; a low primary 

 or a demi-plate may or may not form the lowest part of the com- 

 bination. 



Interradia with many or few vertical rows of primary tubercles 

 and secondaries. 



Peristome small; branchial incisions well developed. Spines 

 slender, long, subcylindrical, striated longitudinally, sharp. 



Fossil. Cretaceous : Europe. Eocene : Europe, Asia, Egypt. 



Subgenus Gagaeia, Buncan. 



Syn. Micropsis (pars). 



Tests with two vertical rows of primary tubercles in each area, 



