﻿PROM THE UPPER GREENSAND. 



241 



buccal pores, some double externally, others small internally. Ambulacra narrow, 

 sub-petaloid, straight, more or less elongated, and open at the lower extremity ; poriferous 

 zones composed of an inner series of round pores, and an external series of elongated 

 pores arranged in conjugate pairs (fig. 2 g) ; tubercles very small, raised on mammillated 

 bosses (fig. 2) in many horizontal lines on the surface of the dorsal plates, those at the 

 base being larger. Apical disc small, prominent, formed of four perforated ovarial plates 

 and five microscopic oculars, the madreporiform body projecting from the surface 

 (fig. 2/). 



Affinities and Differences. — Catopygus differs from Clypeopygus and Echinobrissus by 

 its oval form, convexity of the upper surface, inflation of the sides, and flatness of the base, 

 by its pentagonal mouth, with five prominent sides and rosette of pores between the 

 lobes, and its small round periprocte opening high in a prominent vertical truncation of 

 the single inter-ambulacrum. 



The genus Catopygus appertains to the Cretaceous rocks, and is a very characteristic 

 fossil in its different divisions. In the Gault or Albian stage of the Mediterranean basin 

 Catopygus cylindricus has only hitherto been found. 



In the Upper Greensand or Cenomanian formation C. columbarins prevails throughout 

 the Anglo-Parisien and Mediterranean basins. 



In the Lower Chalk or Turonian C. Ebrayanus is found. 



In the Middle Chalk or Senonian eight species have been collected in Erancc, where 

 many of the beds of this division attain a development unknown in England, and contain 

 a fauna of the most remarkable forms. The C. sub-carinatus and elongatus are found 

 simultaneously in the Anglo-Parisian and Pyrenean basins, although C. Icevis, fenes- 

 trates, con f or mis, pyr if or mis, obtusus, and affinis, are discovered only in the Parisian basin. 



This genus, therefore, attained its greatest development in the seas which deposited 

 the White Chalk with flints, and became extinct with the close of the Cretaceous epoch, 

 as Catopygus is not found in the Tertiary rocks nor in the waters of the present 

 time. 



Catopygus columbarius, Lamarck, 181 G. PI. LV, fig. 2 a — i. 



Echinites pyriformis, Parkinson. Organic Remains, vol. iii, tab.'iii, fig. 6, 1811. 

 Nucleolites columbaria, Lamarck. Anim. sans Vertebres, t. iii, p. 37, 1816. 



— — Deslongchamp. Encyl. Method., t. ii, p. 570, 1824. 



— — Befrance. Die. des Sciences Nat, t. xxxv, p. 313, 1825. 



— carinatus, Gotdfuss. Petrefacta Germanise, b. i, p. 142, pi. xliii, fig. 



11, 1826. 



— columbaria, Blainvil/e. Die. des Sciences Nat., t. lx, p. 188. 1830. 



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