GENEEA AND GEOUPS OF THE ECHIlSrOIDEA, 185 



Genus Catoptgus, Aqassiz, 1836, Frodr. d''une Monogr. des 

 Badiau-es, p. 185 ; 1847, Cat. Bais., Ann. Sci. Nat. vol. vii. 

 p. 157. Cotteau Sf Triger, 1839, Ech. de la Sarthe, p. 184. 

 Desor, 1858, Synopsis.^ p. 282. Lauhe, 1869, Sitzungsh. 

 AJcad. Wiss. Wien, vol. lix. Bd. 1, p. 190. Studer, 1880, 

 Monatsb. d. Tc. preuss. Akad. zu Berlin, p. 861. A. Agassiz, 

 1881, 'CJialleiiger'' Beport, p. 123. Duncan, 1887, Quart. 

 Journ. Geol. Soc. vol. xliii. p. 420. 



Syn. Oolopygus, d'Orb. 



Small and moderate- sized Urclims, often cylindroid, longer than 

 broad, rather low, tumid in front, rather keeled on the hinder 

 part of the abactiual surface, truncated vertically posteriorly, 

 where the periproct is high up, usually at the end of a groove and 

 below the end of the keel. Actinally the test is rather swollen. 

 Peristome excentric in front, pentagonal, elongate longitudinally, 

 with phyllodes and bourrelets. 



Apical system excentric in front ; four perforated basal plates, 

 the fifth absent ; madreporite large, separating the posterior 

 basal plates ; radial plates small. 



Ambulacra narrow, subpetaloid, nearly flush, continuous, with 

 a pair of round pores in each plate as far as the peristome. 

 Pores unequal ; the outer of a pair more or less elongate. 

 Granulation very close. 



Fossil. Cretaceous : England, Europe, Asia. 



I consider that certain Tertiary forms as well as some recent 

 species vvhich have been associated with this well-marked genus 

 should come within the subgenus Studeria. 



A. Agassiz described and figured Catopygus recens, which was 

 dredged by the ' Challenger ' (Eeport on the ' Challenger ' Echini, 

 1881, p. 123) ; and Studer described C. Loveni from the seas to 

 the south of the Cape of Good Hope, in the description of the 

 ' Gazelle ' Echinoidea, 1880. Both depart from the Cretaceous 

 type ; and A. Agassiz notices the uniporous condition of the 

 ambulacra below the petaloid part, as well as tlie elongate nature 

 of the outer pores of the pairs within it. 



Subgenus Sttjdeeia. 



The test is the same as that of Catopygus in shape, peristome, 

 and periproct ; but the ambulacra have only one pore in each 

 plate in a poriferous zone below the subpetaloid portions. 



