72 



S. LOVEN, ON roURTALESlA, A HENUS OK ECIIINOIDEA. 



Mncropnenstes Pellat 



COTTEAV. 



Prenaster Jutieri 

 Desor. 



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

 will appear, to assnnic the modified strueture of the calyeinal system, the costal 5 also 



keeps within its preoincts, while the reduced press of 

 the filter on the c-ostal 2 admits of the normal pres- 

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

 genera of låter appearance, while this pore is con- 

 stantly maintained, the duster of water-pores is seen 

 to have withdrawn from this costal and to have retreat- 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 reaehing beyond the posterior 

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

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

 Brissus, Metalia, Rhinobrissus, Cionobrissus, Meoraa, Spatangus, Homolampas, Palteo- 

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

 Eupatagus. among the Prymnodesmians. 



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

 Ethmolysii, 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 South 

 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 tirst was referred by L. Agassiz to Agas- 

 sizia Val., while Troschel, 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 : Tripj^lus. For the two other, Tr. cavernosus Phil. and Tr. australis 

 Phil., placed bv L. Agassiz in Brissopsis, b}- Gray in Faorina, Troschel created a new 

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



') Étiuies p. 12, Pl. XII, iio-. 100, 101, Brissopsis; 106, Meoma; 107, Echinociirdimti. 

 -) The tollowing is the uomenclatural historv of the species of 



Abatus Troschel. 

 VVieirraanns Archiv. XVII, (1851), 72. 

 1. Abatiis cavernosus Phimppi. 

 1845. Tripylus cavernosus Phil. Wo;m. Arch. XI, 345, t. XI, 



Brissopsis 

 Faorina 



Heniiaster 



1845. Tripvlus australis Pun,. 

 Brissopsis » > 



Faorina » » 



Hemiaster » " 



1847. Ag.\ss. a Des. Cat. R., Ann. 8c. Nat., 3:e Sér., VIII, 15, sep., 121. 



1851. Ge.\y, An. Nat. Hist., 2:(1 ser, VII, 1.32. 



1855. Gray, Cat. rec, Ech. Br. Mus., 57. 



1872. Al. AoASSiz, Rev. Echin., 132, 587, t. XXI c, f. 1, 2. 



1876. Al. Agassiz, Proc. Am. Ac. Arts a. Se. Boston, XI, 231. 



1879. Edc. a. Smith, Phil. Träns., Vol. 168, 271. 



1880. Studee, Zoolog. Anzeiger, 544. 



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



1881. Al. Agassiz, Rep. Chall. Echinoidea, 179, pl. 20, a. 

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



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



1855. Gray, Cat. Br. Mus., 57. 



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



