FROM THE WHITE CHALK. 67 



(Seine-Inferieure), Fourneaiix la Madeleine (Eure), Saint-Parres pres Troyes (Aube), Eltage 

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

 (Marae). 



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

 name C. hirudo. 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 trtmcatis ; 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. Bixon, Geol. of Sussex, p. 339, pi. xxiv, fig. 25, 1850. 



CiDABis Dixoni, Cotteau. Paleontologie Fran9aise, 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, altliough 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, l^ths of an inch ; 

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

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



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

 by the Rev. T. Wiltshire, F.G.S., whose 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 

 Willett, Esq., F.G.S. M. Cotteau records two specimens from the Etagc Cenomanien, 

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



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



CiDAKIs PLERACANTHA, Jyassi:. Catal. Syst. Ectyp. Foss., p. 10, 1840. 

 — — Sorignet. Oitrsiiis foss. dc I'Eure, p. !, 18.")0. 



