FROM THE UPPER CHALK. 139 



(Charente-Inferieure) measures two and a half inches in diameter, and one incli and 

 one tenth in height. 



The Enghsh specimens of this Urchin that have hitherto been collected are small 

 and immature, they consequently have fewer tubercles in each row than the French 

 specimens possess, and the poriferous zones, for a like reason, have the pores in single file, 

 the bigeminal arrangement being a character of more mature age. 



JJfi/iities and Differences. — This species difTers so much from its Enghsh congeners 

 that it is readily distinguished from all of them by its wide arabital areolae and large 

 tubercles, and the series of small tubercles on the upper surface, with a secondary row on 

 the zonal side. In its general characters C. magyiificum resembles C. Archiaci from the 

 same stage, but the latter has a more pentagonal test, wider inter-ambulacral areas, 

 smaller primary tubercles, and four rows of secondary tubercles ; the base likewise is 

 flatter, and the mouth-opening larger and more superficial. 



Locality and Stratigrapldcal Position. — The English specimens have been found only 

 in the Upper Chalk at Norwich, where they are extremely rare. 



M. Cotteau states that this species is common in the Etage Senonien inf. at Saint- 

 Pierre de Cheville, Saint-Paterne, Saint-Calais, Marcon (Sarthe) ; Villers, Villedieu (Loir- 

 et-Cher) ; Saint-Christophe, Semblan9y (Tndre-et-Loire) ; Barbezieux, Aubeterre, Espagnac, 

 pres Angouleme, Charmant, Lavalette (Charente) ; Royan, Talmont, Saintes, Cognac 

 (Charente-Inferieure), Saint-Georges pres Perigueux, Tretissac (Dordogne) ; Belbeze 

 (Haute-Garonne). 



History. — The table of synonyms gives the history of this species, which was unknown 

 to my old friend Professor Forbes, who named the only specimen he ever saw after the 

 friend who communicated it for description. 



Cyphosoma Wetherelli, Forbes. PL XXVII, figs. 1, a — h. 



Cyphosoma Wetherelli, Forbes. In Morris's Catalogue of British Fossils, 2nd ed., 



p. 75, 1854. 

 — — Woodward. Mem. Geol. Surv., Decade V, Supplement, 



p. 2, 1856. 



Test circular, inflated at the sides, depressed at the summit, and flat beneath ; ambu- 

 lacra wide, two rows of large tubercles, nine to ten in each, gradually diminishing in 

 size towards the poles ; inter-ambulacra, two rows of primary tubercles, nine in each, 

 with a small secondary tubercle in the centre of the zonal margin of each plate; poriferous 

 zones narrow, undulated; pores unigeminal throughout; mouth-opening one third the 

 diameter of the test ; discal opening large, angular, pentagonal. 



Dimensions. — Transverse diameter one inch ; height half an inch. 



Description. — This Urchin very much resembles C. coroUare, Klein, but was separated 



