(JENEEA AND GEOTTPS OF THE ECHINOIDEA. 191 



separating the postero-lateral basal plates ; the radial plates small, 

 the posterior pair separated by the madreporite. 



Ambulacra narrow or broad, petaloid to varying distances 

 from the margin ; the pores of a pair differing in shape, conju- 

 gate, the pairs separated by ornamented costee ; some poriferous 

 zones unequal in length to their fellows, tending more or less to 

 close or not. Beyond the petaloid parts the pores are in single 

 series and small, until the peristome is reached, where tliey 

 develop a feeble phyllode. Interambulacra large, with higher 

 and fewer plates than the ambulacra. 



Peristome slightly excentric in front, or subcentral, or central, 

 pentagonal, with feeble bourrelets and phyllodes. Periproct 

 elliptical, transverse, inframarginal, close to the posterior edge of 

 the test. Tubercles of both areas very equal, small, very uniform, 

 in sunken scrobicules, with miliaries. Spines small, short, forming- 

 tufts near the peristome. 



Fossil. Eocene : Europe, Asia, Africa, W. Indies. Oligocene : 

 Asia. Miocene : Asia, Australia, Europe, "W . Indies. 



Mecent. lied Sea, Moluccas, East-Indian Islands, Australia, 

 Cape of Grood Hope, Senegal, Caribbean Sea. 



Subgenus Milletia. 



Peristome pentagonal, elongate longitudinally, barely sunken. 

 Periproct irregularly circular in outline, close to the posterior 

 edge, and somewhat oblique yet inframarginal. 



Ambulacra broad, unequal, very open ; poriferous zones nearly 

 equal. 



The type is Echinolampas (Milletia) elegantidus, Millet, 1854, 

 Pal. de Maine-et-Loire, p. 178, redescribed by Cotteau, 1883, 

 Bull. Soc. Zool. de Prance, vol. viii. p. 458, pi. xv. figs. 6-8. 



Fossil. Europe ? 



In consequence of Zittel's discovery of the jaws of Conoclypeus, 

 it became necessary for A. Agassiz to take his species G. Sigslei 

 out of that genus and to establish one which would include 

 it. This led to the description of the genus Conolampas, A. 

 Agass., 1883. De Loriol found that some forms which had been 

 considered to belong to Gonoclypeus, but which he showed had 

 neither perignathic girdle nor jaws, had a decided phyllode at 

 the peristomial margin of each ambulacrum. Por these forms 



