204 pnor. p. m. dfncan's eetision of the 



simplicity of the ambulacra cliaracteristic of Asterostoma, 

 Agass. 



The terminology appears to be : — 



Asterostoma excentricum, Lrak., sp. 



„ cuhense, Cott. 



Pseudasterosto7na Jimenoi, Cott., sp. 



Genus Metapoehinus, Michelm, 1854, Bev. et Mag. de Zool. 

 ser. 2, p. 439 ; Bull. Soc. Q'eol. de France, ser, 2, t. i. p. 270. 

 Desor, 1858, Synopsis,*-^. 210. Cotteau, 1860, Pal. Frang., 

 Terr. Jura, vol. ix. pp. 28 & 504. Gotteau, Peron iSf Gau- 

 thier, 1876, Ech.foss. de V Alger, fasc. 2, p. 17. 

 Test of moderate size and large, oval, slightly longer than broad, 

 subcordiform, sometimes dilated at the ambitus. Very tall, gib- 

 bous, and projecting upwards anteriorly, and grooved and oblique 

 bebind, sloping at the sides, actinally tumid, especially behind 

 the peristome. Anterior groove variable. 



Apical system excentric in front, elongate, partly compact and 

 disconnected and posterior. The four basal plates in contact and 

 the posterior radial plates widely separated. The anterior radial 

 plate may separate the antero-lateral basals. 



Ambulacra, bivium disconnected from the trivium ; diverse, 

 apetaloid, flush, except the anterior, and this in a more or less 

 defined groove, with simple, small, distant j^airs of pores; paired 

 ambulacra flexuous, pairs of pores becoming distaut at the am- 

 bitus and numerous near the peristome ; pores comma-shaped, 

 placed obliquely to one another, or circular. 



Postero-lateral iuterradia either uniting along the median line 

 above or having plates intercalated there. 



Peristome excentric in front, transversely elliptical-subun- 

 dulate at its margin. Periproct supramarginal, either flush or 

 in th.e upper part of a groove, and sometimes beneath an expan- 

 sion of tbe test, oval or pyriform, acuminate above. Tubercles 

 very small, crenulate and perforated, subscrobiculate j gt anulea 

 small, homogeneous, especially abactinally. 



Fossil. Jurassic and Cretaceous : Europe. Tithonian : N. 

 Africa. 



