FROM THE WHITE CHALK. 67 



(Seine-Inferieure), Fourneaux la Madeleine (Eure), Saint-Parres pros Troyes (Aube), fitage 

 Senonien Inferieure, Etretat (Seine Inferieure), Tartigny (Oise), Chalons-sur-Marne 

 (Marne). 



History. — The Abbe Sorignet in 1850 described a spine of this species under the 

 name C. Mntdo. The same year the test was well figured with its spines attached 

 by the late Mr. F. Dixon, and described by the late Professor Forbes as C. sceptrifera 

 var. spinis truncatis ; subsequently it was found that Mr. Dixon had given it the MS. 

 name C. sulcata, under which name it appeared in the second edition of the ' Catalogue of 

 British Fossils/ and in Dr. Woodward's notes on Cidaris in the Fifth Decade of the 

 'Memoirs of the Geological Survey.' The Abbe Sorignet's name has been properly 

 retained by M. Cotteau in his continuation of D'Orbigny's Paleontologie Fran^aise. 



Cidaris Dixoni, Cotteau. PI. XI, fig. 4 ; PI. XII, fig. 6. 



CiDAKis. Dixon, Geol. of Sussex, p. 339, pi. xx'iv, fig. 25, 1850. 



Cidaris Dixoni, Cotteau. Paleontologie Fran^aise, torn, vii, p. 238, pi. 1051, fig. 78, 1862. 



The test of this fine Urchin is unknown. 



Description. — Spine very large; stem thick, oblong, glandiform, much enlarged in the 

 middle, and tapering towards the neck and apex ; the lower part is covered with convex, 

 scale-like plates, arranged without much regularity ; in the middle part they are larger, 

 and have much the same character ; at the upper third they are less closely set together, 

 become ridged, and form granulated lines, which pass towards the summit ; the intervening 

 valleys are covered with fine longitudinal lines . 



The neck is short and smooth, although there are traces of longitudinal lines ; the 

 milled ring is not prominent, and the articular cavity indicates a small tubercle ; the rim 

 of the acetabulum is smooth. 



Dimensions. — Length of the entire spine, from acetabulum to apex, li^ths of an inch ; 

 length of neck and head ^ths of an inch; length of stem l^^ths of an inch; thickness of 

 stem, at widest part, 4.ths of an inch. 



Locality and StratiyrapJiical Position. — Found in the Grey Chalk near Folkestone 

 by the Rev, T. Wiltshire, F.G.S., Avhose cabinet contains a very fine specimen. Mr. 

 Dixon's type, which formed the subject of fig. 4, PI. XI, is in the collection of Henry 

 W^illett, Esq., F.G.S. M. Cotteau records two specimens from the Etage Cenomanien, 

 at Havre (Seine Inferieure), where it is very rare. 



Cidaris pleracantha, Agassiz. PI. XI, fig. 5 ; PI. XII, fig. 5. 



CiDAiiis PLERACANTHA, Agassxz. Catal. Syst. Ectyp. Foss., p. 10, 1840. 

 — — Sorignet. Oursins foss. de I'Eure, p. 4, 1850. 



