of the Ventriculidse of the Chalk. 89 



que latere porosum." The characters of Ocellariay as given by 

 all the authors*, are clear and unmistakeable so far as they go; 

 and there cannot be a moment's doubt as to what the true rela- 

 tions of the so-called genus are, as will presently be seen. It is 

 perfectly certain that this so-called Ocellaria ramosaf has none 

 of these relations, and therefore that it does not serve to bring 

 the Ventriculidse within the tertiary period. No trace of this 

 family has, then, yet been anywhere discovered higher than the 

 upper beds of the English chalk. 



As it is desirable to have the treatment of the subject as com- 

 plete as possible, so far as it goes, and as the materials which I 

 have collected from the English chalk are sufficiently abundant 

 to lead me to hope that such completeness may be given, for all 

 practical purposes, to the description of the forms found in those 

 beds, I shall confine myself at present to these last ; which I the 

 rather do in that, while it would be a priori probable that the 

 examination of so extensive a series of beds would at any rate 

 afford a full series of typical characters, — and therefore a sound 

 basis for a permanent and generally applicable system of classifi- 

 cation, — the examination of the Rhanden specimens in the British 

 Museum has satisfied me that all of them will range within the 

 typical groups which the forms of the English chalk have led me 

 to assign. 



I have already indicated J in what direction we must look for 

 the essential characters which mark this whole family. It is 

 extremely improbable that a structure so extraordinary, so pecu- 

 liarly bearing the marks of special design and adaptation as 

 the octahedral structure, should be otherwise than characteristic 

 of the family in individuals of which its existence has been dis- 

 covered. Until, then, it has been found elsewhere, the philoso- 

 phical inquirer will take that structure as his guide in the deter- 



* Those characters are, ''Polypier pierreux, aplati en membrane, diverse- 

 ment contourne, subinfundibuUforme'e, a superficie arenacee, muni de pores 

 sur les deux faces." The observations of Milne-Edwards, on an inspec- 

 tion of the actual fossils, are alone sufficient to show that the present fossils 

 could not be Ocellari(B, their apparent tubules being, as stated in p. 511, 

 sometimes penetrated by fibres in a radiated manner. Milne-Edwards 

 expressly says (Lamarck, Anim. sans Vert. ii. p. 291), " L'axe solide, qui 

 remplit assez ordinairement les trous, et qui a ete pris pour une partie du 

 Polypier lui-roeme, n'est que la gangue qui s'est moulee dans ces trous, et 

 qui s'est cassee au niveau de la surface du Polypier, lorsque celui-ci a ete 

 detache de la masse qui le renfermait." 



t The fossil is however a very curious and interesting one. Its whole 

 aspect and character recall those of the Alcyonium, both in its massiveness, 

 its cylindrical tubules, and their connecting plexus of fibres. I have many 

 analogous fossils from the chalk, into the investigation of which it is my 

 intention to enter when the present subject shall be completed. 



I Ante, vol. xx. p. 182. 



