﻿394 



PYGURUS 



from that species by the following characters, " Par sa forme plus oblongue, plus allongee, 

 par ses ambulacres relativement plus larges, se retrecissant moins brusquement et loges, aux 

 approches du peristome, dans des sillons plus droits et plus prononces, par sa face inferieure 

 moins dcprimee. Ces deux especes caracterisent d'ailleurs un horizon different ; le Pygurus 

 Michelini, propre aux couches de la Grande Oolite, se rencontre associe a V Echinobrissus 

 clunicularis, au Collyrites ovalis, a V Hyboclypus gibberulus, tandis que le Pygurus depressus 

 se trouve dans le Kelloway ferrugineux avec le Collyrites elliptica, I' Echinobrissus Gold- 

 fussii, le Pseudodiadema Calloviense, etc."* 



Pygurus Michelini, Cott., resembles Pygurus pentagonalis, Phil., in its general outline ; 

 the former, however, is more depressed on the upper surface and more undulated at the 

 base, the anterior border is more concave, and the single inter-ambulacrum more 

 rostrated and deflected. 



Locality and Stratigraphical position. — I found one small example of this species in 

 the Great Oolite at Minchinhampton, where it is excessively rare. I have collected 

 beautiful specimens in the Cornbrash near Trowbridge, Wilts, and my kind friend, the 

 Rev. A. W. Griesbach, presented me with the magnificent specimen figured at PI. XXXV, 

 which he obtained from the Cornbrash at Rushden (Northamptonshire). I have two 

 inferior specimens from the Cornbrash near Yeovil. The specimen of this species I 

 first figured was said to have been found in the Lower Trigonia Grit (zone of Ammonites 

 Parkinsoni) at Shurdington Hill, near Cheltenham. This urchin has been collected from 

 a marly bed of Cornbrash near Fairford ; it was found by my friend, J. Lowe, Esq., in 

 the Cornbrash at Wincanton (Somerset), and I have seen specimens which were obtained 

 from the Bradford clay at Bradford, Wilts. It seems therefore that the range of this 

 species, like many other Echinodermata which first appeared in the zone of Ammonites 

 Parkinsoni, Inferior Oolite, extended onwards through Fuller's earth, Great Oolite, 

 Bradford clay, and Forest marble, into the Cornbrash, in which formation they all became 

 extinct. 



The foreign distribution of this Pygurus is the same as in our English Oolites. M. 

 Bouchard-Chantereaux kindly sent me a specimen which he collected from the Great Oolite 

 near Boulogne-sur-Mer. 



It has been collected by M. Triger at " Monne (carriere de Bernay), La Jauneliere, 

 Hyere, Noyen, Pecheseul, route de Coutilly, route de Sure a Mortagne. 



" Tabl. de M. Triger, Bradford Clay, Ass. No 1, et Forest marble, Ass. No. 4." 



It has been found by M. Cotteau in the " Grande Oolite de Asnieres, Chatel- 

 Gerard (Yonne)," and by M. Desor in the " Marnes Vesuliennes du Jura Soleurois et 

 Argovien."f 



* Cotteau et Triger, ' Ecliinides du departement de la Sarthe,' p. 67. 

 t Ibid. Ibid. p. 67. 



