FROM THE WHITE CHALK. 271 



Posterior border narrow, obliquely truncated downwards and inwards, and slightly 

 concave transversely. 



Vent located in the upper part of the border under a ridge-like projection of the 

 dorsal surface. 



Periprocte oval and widely patent. 



Pasciole sub-anal, forming a ring around the posterior extremity ; embracing half 

 of the upper and half of the lower part of the border. 



Tubercles perforated sparsely, distributed on the upper surface ; larger and placed 

 closer together below. All are raised on bosses with crenulated summits. 



Spines small, needle-shaped, straight or bent, and enlarged and crenulated at the 

 base. 



Micraster differs from Epiaster in possessing a well-defined sub-anal fasciole, and 

 from Hemiaster and Periaster by the absence of a peripetalous fasciole. 



Micraster forms a leading genus of fossil Urchins, and well characterises the upper 

 beds of the Cretaceous formation in the Anglo-Parisian, Pyrenean, and Mediterranean 

 basins of Europe. 



Micraster cor-anguinum, Klein, sp., 1734. PI. LXII, figs. 1 a — /, 3, 5 (not fig. 4). 



Brontia vel Ombria, Plot. Nat. Hist. Oxfordshire, p. 91, pi. ii, fig. 11, 



1677. 

 Echinites prater rauios, Lister. De Lapidibus Turbinatis, p. 224, fig. 28, 



t. vii, 1678. 

 Echinites cordatus vulgaris, Llhwyd. Lithophylac. Britannici Iconograph, p. 47, 



Num. 964—967, fig. 964, 1699. 

 Echinospatagus cordiformis, Breynius. Schediasma de Echiuis, p. 62, t. v, figs. 



5,6, 1732. 

 Spatangus cor-anguinum, Klein. Naturalis Dispositio Echinodermatum, p. 28, 



t. xxiii, figs, a — d, 1734. 



— — Klein. Ordre Nat. des Oursins de Mer ; ed. Gall., 



p. 100, pi. xii, figs. E, p, pi. xiii, fig. c, 1754. 



— — Leske. Addit. ad Kleinii Disposit. Echinid., p. 221. 



pi. xxiii, figs, a — D, pi. xxiii* c, and pi. xlv, fig. 12, 



1778. 

 Echinus cor-anguinum, Gmelin. Systema Naturae, p. 3195, No. 91, 1799. 



Spatangus cor-marinum, Parkinson. Organic Remains, vol. iii, p. 28, pi. iii, 



fig. 11, 1811. 



— cor-anguinum, Lamarck. Anim. sans Vert., t. iii, p. 32, 1816. 



— punctatus, Lamarck. Ibid. 



— cor-anguinum, Deslongchamps. Encyl. Method., t. ii, p. 63, 1824. 



— punctatus, Deslongchamps. Ibid. 



— cor-anguinum, Defrance. Diet. Sc. Nat., p. 93, t. 1, 1827. 



— punctatus, Defrance. Ibid. 



