140 PEOF. P. M. DTTKCAN's REVISION OF THE 



Apical system with the madreporite in basal plate No. 2 only. 



Ambulacra with greatly crowded low primary tubercles. 



Interradia crowded with small tubercles, the line of the trans- 

 verse coronal sutures furrowed. Eibbing of plates within slight. 

 Perignathic girdle ill developed. 



Fossil. Cretaceous : England, Europe. 



Genus Conocltpeus, Aqassiz, 1839, Ech. Suisse, vol. i. p. 63. 

 Desor, Synopsis, 1858, p. 318. Ziitel, 1879, Hanclh. d. Pal. 

 vol. i. pp. 515-516. Be Loriol, 1880, Monogr. des Ech. 

 Ntvmm. de TEgypie, p. 80 ; P alceontograpliica, 1881, Eoccine 

 Ech. aus ^gypt. u. d. Lib. Wiiste, p. 14. Duncan Sf 

 Sladen, 1882, Pal. Ind. ser. xiv., J^oss. Ech. W. Sind, pp. 51, 

 94, 124. A. Agassiz, 1883, 'Blahe ' Ech. p. 49 (Amejided.) 



Test large, thick, more or less oval in marginal outline, conical, 

 vaulted, swollen or subcorneal dorsally, rather flat actinally, rising 

 somewhat suddenly from the margin. 



Apical system central or slightly excentric in front, small, 

 projecting, with four basal plates ; the madreporite in the right 

 anterior basal, intruding also on the other basals, occupying 

 the centre of the system, and separating the posterior radial 

 plates; five small radial plates. 



Ambulacra long, open, with broad poriferous zones nearly 

 as far as the ambitus, thence gradually diminishing in breadth 

 to the peristome, flush, or slightly sunken, or raised. Plates 

 numerous low and broad primaries, rarely some demi-plates 

 near the peristome. Pores wide apart and in pairs where the 

 zones are broad, the inner pore circular in outline, and the 

 outer more or less elliptical or comma-shaped ; pairs gradually 

 increasing in breadth and then diminishing, separated by costae. 

 Below the parts of the ambulacra with paired j)ores others are 

 continued to and over the ambitus to the peristome, as a single 

 series, a pair rarely being seen near the peristome and then it 

 is due to the presence of a demi-plate. Phyllodes do not exist. 

 Interporiferous areas broad, often projecting. 



Interradia large, but narrow at the summit, and consisting of 

 broad plates which are much higher than those of the ambulacra; 

 projecting into the peristome. 



Peristome central, moderate, pentagonal, elongate transversely, 

 with well-marked bourrelets and no phyllodes. A ring-like 



