FROM THE WHITE CHALK. 51 



forms of the spines in different regions of the shell, and the series of figures between 

 3 and 23 shows some of the extreme shapes these appendages assume. 



Affinities and Differences. — This urchin is readily distinguished from other species of the 

 White Chalk by its small test, equally depressed at both poles, narrow areolae, prominent 

 imperforate tubercles, and large claviform spines, more or less elongated, and covered with 

 spinous ridges. In this respect it resembles C. Bowerbankii, Forb., PI. II, fig. 1, from 

 which it is distinguished chiefly by the character of the spines, and the larger size of the 

 inter-ambulacral tubercles. Compare PI. II, fig. 1, a, with PI. IV, fig. 1. 



LocaJity a7id Sfrafiyrapliical Position. — This is the most common Cidaris in our 

 White Chalk ; it is found at Woolwich, Gravesend, Lewes, Brighton, and in the same 

 formation in Wilts and Dorset. The specimens figured in Pis. IV and V were found 

 near Woolwich, and developed by the late Mr. Taylor. The grand s[)ecimen figured in 

 PI. IV is in the possession of Dr. Bowerbank, that in PI. V, showing the dental apparatus, 

 peristomal plates, and apical disc, belongs to the British Museum. 



It is very abundant in the Etage Senonien of France, and found, according to M. 

 Cotteau, at Dieppe, Fecamp, Tancarville (Seine-Inferieure) ; Falaise (Somme) ; Vernonnet, 

 Giverny, Clachaloze, Petit-Andelys, Pinterville pres Louviers, Hougue-marre, Sinneville 

 (Eure) ; Notre-Dame-du-Thil, Mory la Herelle, le Mesnil-Saint-Fermin, Pouilly La- 

 boissiere (Oise) ; Maintenon, Chateau- GaiUard (Seine-et-Oise) ; le Mesnil-Saint-Thomas 

 (la Poterie) (Eure-et-Loire). 



History. — This urchin was first figured and described by De Luc in 1763, and after- 

 veards by Leskeand Parkinson ; in 1823 by Mr. Koenig, in Mantell's ' Geology of Sussex,' 

 who named it C. davigera. The first accurate description of the test and spines was made 

 by M. I'Abbe Sorignet, who pointed out the size and imperforation of its tubercles as 

 important diagnostic characters. It has recently been well figured by M. Humbert for 

 M. Cotteau in the ' Paleontologie Fran9aise ;' and Mr. Bone has given most ample details 

 from all the best English specimens that I am acquainted with. 



Cidaris serrifkra, Forbes, 1850. PI. XI, fig. 1, a, b, c, d, e,/, r/, h, fig. 6. 



CiDAius CLAVIGERA, Revss. Versteinerungeii der Bohmischen Kreidef., p. 57, pi. 

 x.\, fig. 21, 1845. 



— SEiiRirERA, Forbes, in Dixon's Geo), and Foss. of Sussex, p. 338, pi. xxiv, 



figs, 15 — 19, and pi. xxv, fig. 2, 1850. 



— PUNCTILLUM, Sorignet. Oursins Foss. de I'Etire, p. 9, 1850. 



— SEKEIFERA, Forbes, in Morris's Cat. of Brit. Foss., 2nd ed., p. 75, 1854. 



— PUNCTILLUM, Desor. Synopsis des Echinides Foss., p. 15, 1856. 



— — lhijari/i?i et Hup^, Zoophytes ; fichinodermes, p. 481, 1862. 



— SEKRTFERA, Cotteau. Paleontologie Fran9ai8e ; Ter. Cret. ; Ecbinides, torn. 



ii, p. 293, pi. 1071, figs. 5—15, 1863. 



