72 



S. LOVEN, ON POURTALESIA, A GENUS f(F EOHTNOIDEA. 



Mueropneustes Pellat 



C'OTTF.AL'. 



Preuaster Jutic* 

 Uksok. 



duct of the corresponding sexual gland. In Prenaster and Macropneustes, the next, it 

 will appear, to assume the modified structure of the calyciiial system, the costal o also 



keeps within its precincts, while the reduced press of 

 the filter on the costal 2 admits of the normal pres- 

 ence of its sexual pore. But in the great number of 

 genera of later appearance, while this pore is con- 

 stantly maintained, tlie cluster of water-pores is seen 

 to jiave withdrawn from this costal and to have retreat- 

 ed backward, expanding the combined area of the 

 central ossicle and the costal .5, which thus are made 

 to form a prolongation reaching beyond the posterior 

 limits of the calycinal system and far into the interradium 5 '). This is the case in 

 the great majority of recent Spatangidte: Faorina, Agassizia among the Pymnadetes, 

 Brissus, Metalia, Rhinobrissus, Cionobrissus, Meoma, Spatangus, Homolampas, Pala'o- 

 pneustes, Brissopsis, Kleinia, Echinocardium, Plagionotus, Breynia, Maretia, Lovenia, 

 Eupatagus, among the Prymnodesmians. 



The diversity between the calycinal system of tlie Ethmophracti and that of the 

 Ethniolysii, striking as it is, has nevertheless been overlooked. As long ago as in 1845 

 Philippi described and figured three species of Spatangus from the antarctic sea of youth 

 America, and proposed for their reception a new subgenus: Tripylus, principally char- 

 acterised by possessing only three sexual openings. He named them Tripylus excava- 

 tus, Tr. cavernosus, and Tr. australis. The first was referred by L. Agassiz to Agas- 

 sizia Val., while Troschei,, who examined the original specimens of all three, made it 

 the type of a new genus: Hamaxitus, and Gkay and Al. Agassiz retained for it the prim- 

 itive appellation : Tripylus. For the two other, Tr. cavernosus Phil, and Tr. australis 

 Phil., placed by L. Agassiz in Brissopsis, by Gray in Faorina, Troschel created a new 

 genus: Abatus"), remarking at the same time, that if only one species had come under 



>) fitudes p. 12, PI. XII, lif;. 100, lUl, Brissopsis; lOG, Meoma; 107, Ecluiiouardiiiiii. 

 '^) The following is llu' iioineiK-latiiral history of the species of 



Abatus Troschel. 

 VViL'u;mauns .\rchiv. XVll, (ISfjl), 72. 



1845. Tripvliis cavernosus Piui, 

 Biissopsis " " 



Faorina " » 



Heniiaslcr " » 



1845. Tripvlus australis Pmi, 

 Brissopsis " < 



P'aorina " » 



Heniiiister " » 



1. 



W'sni. 

 1847. 

 1851. 

 1855. 

 1872. 



;rnosu3 Phiiippi. 



.\ b a t us c < 



Arch. Xl, :U5, t. XI, f. 2, 



Ao.\ss. 4 Des. Cat. R., Ann. 6c. Nat., .•>:c Ser., VIII, 15, scp., 121. 



Gray, An. Nat. Hist., 2;il ser, Vll, 132. 



Gray, Cat. rec. Ech. Br. Mus., 57. 



Al. Agassiz, Rev. Echin., 132, 587, t. XXI c, f. 1, 2. 



1876. Al. Agassiz, Proc. Am. Ac. .Vrts a. Sc. Boston, XI, 231. 



1879. Edg. a. Smith, Phil. Trans., Vol. 168, 271. 



1880. Stuuer, Zoolog. Anzeiger, 544. 



1880. Studer, Mon. Ber. Berl. Akad. 881. 



1881. Al. Agassiz, Rep. Chall. Echinoidea, 179, pi. 20, <(. 

 1. c. .347, T. Xl, f. 3. 



1847. Agass. et Des., Cat. R. 1. c. 



1855. Gray, Cat. Br. Mns., 57. 



1872. Al. Agassiz, Rev. 132, 586, pi. XXI c. f. 3. 



