FROM THE INFERIOR OOLITE. 869 



mhradiatus. Sow., Slomechinus bigranularis, Larak., Iloledypus hemispharicus, Desor, 

 Collyrites ovalis, Leske, and CoUi/rites rinyetis, Desml. It appears to take the place of 

 Clypeus Flotii in the Parkinson! zone of Dorsetshire, just as Holectypus hemispharicus, 

 Desor, replaces in the same rock in Dorsetshire Holectypus depressus, Lamk., which is so 

 abundant a fossil in this zone of the Inferior OoUte in the Midland counties of England 

 and so rare in the South. 



History. — This, urchin was first described by Professor M'Coy, in his paper on ' New 

 Mesozoic Radiata ;' the species was for a time overlooked, as no figure was given with the 

 description ; Professor M'Coy subsequently kindly sent me pen-and-ink outlines of all the 

 species described in that memoir, by which I was enabled to identify the forms supposed 

 to be new. This Clypeus has recently been beautifully figured, and well described as 

 Clypeus Davoustianus, by my esteemed friend M. Cotteau, in his valuable monograph on 

 the ' Echinides of the Sarthe.' It was not included in my memoir on the * Cassidulidge of 

 the Oolites,' as at the time I could not find a specimen to study. Since the publication of 

 that Prodrome I have collected a very fine series of this species ; a comparison of the 

 figures given by M. Cotteau, and the one now published in our PI. XXVII, fig. 1, leaves 

 no doubt as to the identity of the Sarthe Clypeus Havoustianus, Cot., and the Dorsetshire 

 Clypeus alius, M'Coy, 



Clypeus Michelini, Wriyht. PI. XXX, fig. 2 a, b, c, d. 



Nticleolites Michelini. Wright, Ann. and Mag. of Nat. Hist., 2d series, vol. xiii, p. 161, 



pi. xii, fig. 6, 1854. 

 —^ — Forbes, in Morris's Catalogue o"f Brit. Fossils, 2d ed., additional 



sp. of Echinodermata, 1854. 

 — — Wright, Report Oolitic Echinod., Erit. Assoc. Reports, 1857. 



Clypsds Michelini. Desor, Synopsis des Echinides Fossiles, p. 277, 1858. 



Test circular or oblong, discoidal and mucli depressed, posterior border produced, 

 truncated and slightly deflected in old individuals ; ambulacral areas narrowly lanceolate ; 

 poriferous zones narrow, only slightly petaloid on the dorsal surface, vertex and apical 

 disc nearly central ; anterior half of the upper surface convex, posterior half much declined ; 

 anal valley narrow above, diverging below, extending from the apical disc to the border ; 

 base flat, slightly concave ; mouth excentral, peristome with five small lobes j postero-lateral 

 inter-ambulacral areas slightly tumid at the base. 



Dimensions. — Height, nine tenths of an inch ; antero-posterior diameter, three inches 

 and a quarter ; transverse diameter, two inches and one fifth. 



Description, — The outline of this urchin varies in difierent individuals, and likewise 



