126 On a new Species o/" Nucleolites. 



of the experience of Mr. Alex. Agassiz, who remarks * : — 

 " The mere conjugation of the pores is an insufficient cha- 

 racter, as in specimens of N. epigonus and of E. receiis we 

 find in the same individual a petal in which the conjugation 

 is marked, another where it is indistinct, and frequently the 

 corresponding one in which the conjugation cannot be traced ; " 

 or of the judgment of Prof. E. von Martens f, " Die seichten, 

 schwer erkennbaren Furchen der vorliegenden Art rechtferti- 

 gen eine solche Trennung nicht." Prof. Zittel is not to be 

 congratulated on a step backward from the position taken up 

 by D'Orbigny (Pal. Fran^., Cretac. vi. p. 388), Wright, and 

 others as to the synonymy of Echinohrissus with Nucleolites. 



If, however, we are content to accept the rules of nomen- 

 clature suggested by the British Association we must use 

 Lamarck's name Nucleolites rather than the pre-Linnean 

 (1732) name of Echinohrissus^ which was suggested by 

 Breynius in his remarkable ' Schediasma.' 



But if Zittel's separation of Echinohrissus fVom Nucleolites 

 be so little justifiable, does not the transverse long axis of our 

 new species lead us so near to Rhynchopygus as to suggest 

 the merging of these forms under one genus ? It is difficult 

 to answer this question with certainty ; the form of the peri- 

 proct is, it is clear, not of generic importance ; but the much 

 better development of the oral floscelle and the inequality of 

 the constituent rows of pores in the paired ambulacra show 

 that Hhynchopygus has gone further in the way of differentia- 

 tion than has Nucleolites ; and just as Wright (' Oolitic 

 Echinodermata,' p. 360) keeps, notwithstanding the opinion 

 of E. Forbes, Clypeus distinct from Nucleolites ^ on account of 

 the " magnitude and development of the long, wide, petal- 

 oidal, poriferous zones," so the greater tendency to a petaloid 

 form and that sure sign of differentiation, inequality in length 

 of the zones, would, even without the characters of the mouth, 

 outweigh the value of the form of the periproct. 



It is to be hoped that the structural characters of this new 

 species will be sufficient to attract the notice of the palseon- 

 tologist, who will, I trust, agree that 



(1) Nucleolites and Echinohrissus are synonymous. 



(2) There is nothing to justify even their subgeneric 



division after the discovery of N. occidentalis. 



(3) The form of the periproct and of the actinostome are 

 less important, as signs of differentiation, than the 



* Rev. Ech. p. 557. 



t Arcliiv fur Naturg. xxxii. (1866), p. 180. 



